what type of tissue are bronchioles

n : bronchiole The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which

bronchiole

"definitio

branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system. The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.== Structure ==A pulmonary lobule is the portion of the lung ventilated by one bronchiole.

The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow.

A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow.===Bronchioles===The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi ( tertiary meaning ""third""). The tertiary bronchi subdivide into the bronchioles. They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have club cells in their epithelial lining.

The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium as the bronchioles decreases in size. The diameter of the bronchioles is often said to be less than 1 mm, though this value can range from 5 mm to 0.3 mm.

As stated, these bronchioles do not have hyaline cartilage to maintain their patency. Instead, they rely on elastic fibers attached to the surrounding lung tissue for support. The inner lining (lamina propria) of these bronchioles is thin with no glands present, and is surrounded by a layer of smooth muscle.

As the bronchioles get smaller they divide into terminal bronchioles. These bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, from the sixteenth through the twenty-third division of the tract.

===Terminal bronchioles=== The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells.

bronchiole

"definitio

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system.

Bronchiole

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Please help to improve this article by introducing more precise citations. (May 2015) ( Learn how and when to remove this template message)Bronchiole Diagram of the alveoli with both cross-section and external view. Details System Respiratory system Identifiers Latin Bronchioli Me SH D055745TA A06.5.02.026TH H3.05.02.0.00005FMA 7410 76497, 7410Anatomical terminology [ edit on Wikidata]

The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.

Contents [ hide ]1 Structure1.1 Bronchioles1.2 Terminal bronchioles1.3 Respiratory bronchioles2 Clinical significance2.1 Inflammation3 Additional images4 References5 Further reading6 External links Structure [ edit]A lobule of the lung showing r. b respiratory bronchiole; al. d alveolar duct; a. s alveolar sac; 'a' alveol

us A pulmonary lobule is the portion of the lung ventilated by one bronchiole. Bronchioles are approximately 1 mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5 mm or less in diameter.

Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where gas exchange takes place.

The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow. A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow.

Bronchioles [ edit]The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi ( tertiary meaning ""third""). The tertiary bronchi subdivide into the bronchioles.

They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have club cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium as the bronchioles decreases in size. The diameter of the bronchioles is often said to be less than 1 mm, though this value can range from 5 mm to 0.3 mm.

As stated, these bronchioles do not have hyaline cartilage to maintain their patency. Instead, they rely on elastic fibers attached to the surrounding lung tissue for support. The inner lining ( lamina propria) of these bronchioles is thin with no glands present, and is surrounded by a layer of smooth muscle.

Terminal bronchioles [ edit]The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli.

Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. Club cells are non-ciliated, rounded protein-secreting cells. Their secretions are a non-sticky, proteinaceous compound to maintain the airway in the smallest bronchioles.

The secretion, called surfactant, reduces surface tension, allowing for bronchioles to expand during inspiration and keeping the bronchioles from collapsing during expiration. Club cells, a stem cell of the respiratory system, produce enzymes that detoxify substances dissolved in the respiratory fluid. Respiratory bronchioles [ edit]The respiratory bronchioles are the narrowest airways of the lungs, one fiftieth of an inch across. [1] The bronchi divide many times before evolving into the bronchioles. The bronchioles deliver air to the exchange surfaces of the lungs. [2] They are interrupted by alveoli which are thin walled evaginations. Alveolar ducts are distal continuations of the respiratory bronchioles. Clinical significance [ e

dit]Bronchospasm, a potentially life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. The most common cause of this is asthma. Bronchospasm is commonly treated by oxygen therapy and bronchodilators

The bronchi themselves branch many times into smaller airways, ending in the narrowest airways (bronchioles), which are as small as one half of a millimeter across. The airways resemble an upside-down tree, which is why this part of the respiratory system is often called the bronchial tree. Large airways are held open by semiflexible, fibrous connective tissue called cartilage.

Overview of the Respiratory System

Overview of the Respiratory System By Noah Lechtzin, MD, MHS, Associate Professor of Medicine and Director, Adult Cystic Fibrosis Program, Johns Hopkins University School of Medicine NOTE: This is the Consumer Version.

DOCTORS: Click here for the Professional Version To sustain life, the body must produce sufficient energy. Energy is produced by burning molecules in food, which is done by the process of oxidation (whereby food molecules are combined with oxygen).

Oxidation involves carbon and hydrogen being combined with oxygen to form carbon dioxide and water. The consumption of oxygen and the production of carbon dioxide are thus indispensable to life. It follows that the human body must have an organ system designed to exchange carbon dioxide and oxygen between the circulating blood and the atmosphere at a rate rapid enough for the body’s needs, even during peak exercise.

The respiratory system enables oxygen to enter the body and carbon dioxide to leave the body. The respiratory system starts at the nose and mouth and continues through the airways and the lungs. Air enters the respiratory system through the nose and mouth and passes down the throat (pharynx) and through the voice box, or larynx.

The entrance to the larynx is covered by a small flap of tissue (epiglottis) that automatically closes during swallowing, thus preventing food or drink from entering the airways. Overview of the Respiratory System The windpipe (trachea) is the largest airway. The trachea branches into two smaller airways: the left and right bronchi, which lead to the two lungs.

Each lung is divided into sections (lobes): three in the right lung and two in the left lung. The left lung is a little smaller than the right lung because it shares space in the left side of the chest with the heart. Inside the Lungs and Airways

Smaller airways are supported by the lung tissue that surrounds and is attached to them. The walls of the smaller airways have a thin, circular layer of smooth muscle.

The airway muscle can dilate or constrict, thus changing airway size.3D Model: Inside the Lungs Thousands of small air sacs (alveoli) are at the end of each bronchiole.

Together, the millions of alveoli of the lungs form a surface of more than 100 square meters. Within the alveolar walls is a dense network of tiny blood vessels called capillaries. The extremely thin barrier between air and capillaries allows oxygen to move from the alveoli into the blood and allows carbon dioxide to move from the blood in the capillaries into the air in the alveoli. How Lungs Function The pleura is a slippery membrane that covers the lungs as well as the inside of the chest wall.

It allows the lungs to move smoothly during breathing and as the person moves. Normally, the two layers of the pleura have only a small amount of lubricating fluid between them.

The two layers glide smoothly over each other as the lungs change size and shape. Resources In This Article Biology of the Lungs and Airways Overview of the Respiratory System Chest Cavity Exchanging Oxygen and Carbon Dioxide Control of Breathing Defense Mechanisms of the Respiratory System Effects of Aging on the Respiratory System NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version Was This Page Helpful? Yes No Chest Cavity

The cartilage and mucous membrane of the primary bronchi are similar to that in the trachea. As the branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the smallest bronchioles.

Bronchi, Bronchial Tree, & Lungs

Bronchi, Bronchial Tree, & Lungs Bronchi and Bronchial Tree In the mediastinum, at the level of the fifth thoracic vertebra, the trachea divides into the right and left primary bronchi. The bronchi branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli.

As the cartilage decreases, the amount of smooth muscle increases. The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium. The alveolar ducts and alveoli consist primarily of simple squamous epithelium, which permits rapid diffusion of oxygen and carbon dioxide.

Exchange of gases between the air in the lungs and the blood in the capillaries occurs across the walls of the alveolar ducts and alveoli.

Lungs The two lungs, which contain all the components of the bronchial tree beyond the primary bronchi, occupy most of the space in the thoracic cavity. The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue.

They are separated from each other by the mediastinum, which contains the heart. The only point of attachment for each lung is at the hilum, or root, on the medial side.

This is where the bronchi, blood vessels, lymphatics, and nerves enter the lungs. The right lung is shorter, broader, and has a greater volume than the left lung. It is divided into three lobes and each lobe is supplied by one of the secondary bronchi. The left lung is longer and narrower than the right lung. It has an indentation, called the cardiac notch, on its medial surface for the apex of the heart. The left lung has two lobes.

Each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung. At the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax. The small space between the visceral and parietal pleurae is the pleural cavity. It contains a thin film of serous fluid that is produced by the pleura.

The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the lungs inflate and deflate.« Previous (Larynx & Trachea) Next (Review) »

The epithelium is either columnar or cuboidal. The final branches of the bronchioles are called terminal bronchioles. These have a layer smooth muscle surrounding their lumens. Stimulation of the vagus nerve (parasympathetic) causes the smooth muscle to contract, and reduce the diameter of the terminal bronchioles.

Respiratory | Trachea, bronchioles and bronchi

You are here: Histology Guide > Respiratory Respiratory | Trachea, bronchioles and bronchi The conducting portion is made up of:nasal cavities, nasopharynx, larynx, trachea, bronchii and bronchioles The trachea branches to give rise to two primary (main) bronchii.

These then branch successively to give rise in turn to secondary and tertiary bronchii. These then branch to give rise to several orders of progressively smaller airways called bronchioles, the smallest of which are called terminal bronchioles. These are the last components of the conducting portion of the respiratory system. Terminal bronchioles give rise to respiratory bronchioles, which ultimately lead to the alveoli.

Find out more about the respiratory portion. Trachea The trachea is a wide flexible tube, the lumen of which is kept open by 20 tracheal cartilages, which are C-shaped rings of hyaline cartilage. The gaps between the rings of cartilage are filled by the trachealis muscle - a bundle of smooth muscle, and fibroelastic tissue.

Together these hold the lumen of the trachea open, but allow flexibility during inspiration and expiration. The respiratory mucosa and submucosa are adapted to warm and moisten the air, and to trap particles in muco

us. Mucosa and sub-mucosa of Trachea The respiratory mucosa is made up of the epithelium and supporting lamina propria). The epithelium is tall columnar pseudostratified with cilia and goblet cells.

The supporting lamina propria underneath the epithelium contains elastin, that plays a role in the elastic recoil of the trachea during inspiration and expiration, together with blood vessels that warm the air. The sub-mucosa contains glands which are mixed sero-mucous glands. The watery secretions from the serous glands humidify the inspired air. The mucous, together with mucous from the goblet cells traps particles from the air which are transported upwards towards the pharynx by the cilia on the epithlium.

This helps to keep the lungs free of particles and bacteria.show labels This is a cross section through the trachea, showing the major layers.show labels This is a higher power image of the trachea showing the glands and epithelium in more detail.

Can you classify the epithelium? There are lots of sero-mucous glands in the submucosa layer. The layer of cartilage is not seen here, but instead there is a layer of fibro-elastic connective tissue which runs between the rings of cartilage.

Bronchiishow labels This is a picture of a tertiary bronchus. Compare this picture with that of the trachea: Can you identify the circular layer of smooth muscle, and the cartilage, and some glands in the submucosa? The smooth muscle is used to control the diameter and length of the bronchii - it contracts during expiration to help expel the air.

There is also lots of elastin present in the submucosa, as in the trachea. The epithelium is now tall columnar, not pseudostratified (difficult to see at this magnification) and has very few goblet cells. The trachea branches into two primary bronchii, which branch into secondary and then tertiary bronchii. In the tertiary bronchii, there is less cartilage, and it does not completely encircle the lumen, as shown diagramatically above.

Notice also how the mucosa is folded, and think about how this might change as you breathe in and out. Bronchiolesshow labels This is a picture of a bronchiole. There is no cartilage and no glands. Can you identify the ring of smooth muscle, which is arranged in discrete bundles with a variety of organisations.

The tertiary bronchii branch into bronchioles, which have a diameter of 1mm or less, and the wall structure changes.

The epithelium is made up of ciliated columnar cells in larger bronchioles, or non-ciliated in smaller bronchioles (difficult to see at this magnification). There are no goblet cells, but there are cells called Clara cells. These cells are secretory - they secrete one of the components of surfactant.

Asthma: because the diameter of the bronchioles is reliant on smooth muscle tone, these airways can almost completely shut if the smooth muscles contract strongly, which can happen in an asthmatic attack.

Terminal Bronchioles. This picture shows a Terminal bronchiole (TB in the diagram). Note that this is at a lower magnification than the three pictures above. This is the last part of the conducting portion of the respiratory system, and has the smallest diameter of all (less than 1mm). There is no cartilage, or glands, some smooth muscle is still present, there are no goblet cells.

Visceral muscle cells are found in the organs, blood vessels, and bronchioles of the body to move substances throughout the body. Visceral muscles are also commonly known as smooth muscle due to their lack of striations.

Muscle Cell Types

Click To View Large Image Continued From Above... Skeletal Muscle Skeletal muscle is the most common and widely distributed muscle tissue in the body, making up around 40% of the body’s total mass.

It forms all of the skeletal muscles, such as the biceps brachii and gluteus maximus, and is found in the eyes, throat, diaphragm, and anus. Four characteristics define skeletal muscle tissue cells: they are voluntary, striated, not branched, and multinucleated. Skeletal muscle tissue is the only muscle tissue under the direct conscious control of the cerebral cortex of the brain, giving it the designation of being voluntary muscle.

All conscious movements of the body, including movement of the limbs, facial expressions, eye movements, and swallowing are the products of skeletal muscle tissue. The contraction of skeletal muscles also produces the bulk of the body’s heat as a byproduct of cellular metabolism. The structure of skeletal muscle cells also makes them unique among muscle tissues. Skeletal muscle cells develop from the fusion of many smaller cells during fetal development, resulting in long, straight muscle fibers that contain many nuclei.

When viewed under the microscope, skeletal muscle cells appear to have a striped, or striated, pattern of light and dark regions. These stripes are caused by the regular arrangement of actin and myosin proteins within the cells into structures known as myofibrils.

Myofibrils are responsible for the skeletal muscles’ great strength and ability to pull with incredible force and propel the body. Cardiac Muscle Cardiac muscle cells are found only in the heart, and are specialized to pump blood powerfully and efficiently throughout our entire lifetime.

Four characteristics define cardiac muscle tissue cells: they are involuntary and intrinsically controlled, striated, branched, and single nucleated. Cardiac muscle is considered to be an involuntary tissue because it is controlled unconsciously by regions of the brain stem and hypothalamus. It is also considered to be an intrinsic, or self-controlled, tissue because the normal cardiac rhythm is set by specialized pacemaker cardiac muscle cells in the heart itself.

The cells of cardiac muscle tissue are shorter than skeletal muscle tissue and form a network of many branches between the cells. Intercalated disks of overlapping cell membrane form between the cardiac muscle cells to lock them together tightly and allow the quick passage of electrochemical signals between cells.

The cells do not fuse during development, leaving each cell with a single nucleus. One commonality between skeletal and cardiac muscle is the presence of striations due to the arrangement of actin and myosin into regular myofibrils.

The presence of myofibrils and many mitochondria in cardiac muscle cells provides them with great strength and endurance to pump blood throughout an entire lifetime. Visceral Muscle

The bronchioles are part of the airway passages in the lungs. They are located at the end of the bronchi, the larger, branching airway passages in the lungs, and terminate in the alveoli, tiny circular sacs where oxygen is exchanged with carbon dioxide in the blood.

What are the Bronchioles?

These passageways are distinguished from the bronchi in that they do not contain cartilage or glands. They are responsible for controlling air distribution and airflow resistance in the lungs. The lungs and their structures are part of the respiratory system, which controls breathing and also includes the upper respiratory passages, the nose, throat, and sinuses, and the pharynx and trachea.

Air is drawn into the lungs through the upper respiratory passages until it reaches the alveoli, where the blood is oxygenated. Deoxygenated blood transfers its carbon dioxide into the alveoli, and the carbon dioxide is breathed out through the respiratory passages.

This process helps the blood carry oxygen throughout the body, powering the body's metabolism. The bronchial network, like most of the respiratory passages, contains cilia, small fingerlike cell projections, on their inner surface to help move air through the system. Bronchioles are branching, beginning with the primary bronchioles, which branch into the smaller and more numerous terminal bronchioles, which in turn divide into the respiratory bronchioles.

Each terminal one contains Clara cells, which secrete a protein compound called surfactant that serves to lubricate the passageways, maintaining airflow, and to detoxify harmful substances inhaled into the lungs. Bronchial dysfunction can be the cause of life-threatening disorders. In bronchospasm, the bronchial passages constrict and become narrower, impeding oxygen absorption in the blood.

It's a symptom of asthma, bronchitis, flu, and respiratory tract infections, as well as anaplhylactic shock caused by allergens. Bronchospasms can also result as a side-effect of certain drugs, including beta-blockers and pilocarpine.

They can cause coughing, breathlessness, and hypoxia, or a lack of oxygen in the body. An inflammation of the bronchioles is called bronchiolitis. It is typically a symptom of viral infection, but in one rare and serious form, bronchiolitis obliterans, the passageways become obstructed by fibrous connective tissue. Most bronchial disorders can be treated by oxygen therapy or bronchodilation, or by treating the underlying cause of the disease. Bronchodilation uses either medication or mechanical manipulation to widen the airways in the lungs. Bronchiolitis obliterans, however, is irreversible, and may require lung transplant in severe cases. Ad You might also Like Recommended Related wise GEEK Articles What Is a Terminal Bronchiole? What is Gas Exchange?

What is a Bronchospasm? What is Arteriosclerosis Obliterans? What is Horehound Tea? What is a Bronchoalveolar Lavage? What are Pneumocytes? Ad Discuss this Articleroxytalks Post 2Wow, bronchiolitis sounds like it can be pretty dangerous!

I can't believe it can lead to a lung transplant. I'm happy to hear that it's a rare form of bronchiolitis that leads to something so drastic.

We wouldn't want people needing lung transplants all over the place!Those little bronchioles sure are an important part of breathing!calpat Post 1Thank you for explaining what it is that the bronchioles do. I'm really interested in how the human body works, but I don't remember learning much about bronchioles. I wish I would have paid more attention in school!I knew that bronchitis has more to do with the bronchi, but I thought that bronchiolitis was just another name for bronchitis! Now I know the difference!Post your comments Post Anonymously Loginusernamepasswordforgot password? Registerusernamepasswordconfirmemail

oke.3 Respiratory chambers l Respiratory bronchiole has simple, low columnar or cuboidal bronchiolar and ciliated cells; elastic fibres and smooth muscle support the epithelium's BL. 2 Opening out along the respiratory bronchiole are alveoli, whose openings are ringed by smooth muscle.

HISTOLOGY FULL-TEXT

HISTOLOGY FULL-TEXTWilliam A Beresford MA, D Phil © Professor of Anatomy Anatomy Department, West Virginia University, Morgantown, USAChapter 22 RESPIRATORY TRACTThe tract rhythmically expels spent air and takes in fresh through conditioning passages, conducting it to the respiratory portion of the lungs, where the walls of the air-filled chambers are thin enough to permit an exchange of gases between blood and air.

The respiratory movements involve chemoreceptors, brain centres, the thoracic cage, and various muscles: these structures belong, together with the respiratory tract, in the respiratory system Powerpoint. The lungs also have important metabolic functions not directly related to gas exchange, e.g., the activation of circulating angiotensin I, and the inactivation of some other vasoactive agents.

A RESPIRATORY TRACT TO LUNGSl Nasal cavity l Divided by a hyaline-cartilage nasal septum in the midline. 2 Stratified squamous epithelium (hairy) of the nares changes to 3 a lining nasal mucosa of: .. (a) pseudostratified, columnar, ciliated epithelium with mucus-secreting goblet cells, on .. (b) a loose lamina propria, with many leucocytes, blood vessels, and mixed muco-serous glands.

4 Venous plexuses, to warm the air, underlie the epithelium. 5 Turbinate bones in the conchae support the mucosa.

6 A small part of the mucosa is olfactory, with a neuroepithelium (Chapter l2. B.5.la) and Bowman's glands. 7 Paranasal air sinuses open off the main cavity. 8 The folded pharyngeal tonsil, covered by pseudostratified, columnar, ciliated epithelium, lies posteriorly in the pharynx.9 Nasal functions : (a) air-filtering, material trapped in mucus is swept by the cilia towards the pharynx, (b) air-warming, (c) air-humidifying, (d) olfaction, (e) sensitivity for nasal reflexes such as sneezing, (f) resonating the voice.2 Larynx l Hollow chamber, whose walls are supported by cartilages, connected by ligaments and membranes, and moved by skeletal muscles.

2 The extrinsic and intrinsic muscles move the larynx up and under the epiglottis in swallowing, and move the cartilages and tense the vocal cords during phonation and breathing. 3 The cartilages are hyaline tending to calcification, or elastic for the epiglottis, cuneiforms, corniculates, and the apices and vocal processes of the arytenoids.

4 Mucosa is mostly pseudostratified, columnar, ciliated epithelium with goblet cells, on a loose lamina propria rich in elastic fibres, mucous and mixed glands, leucocytes and sometimes lymphoid nodules. 5 Two constrictions occur: the false vocal cords/ventricular folds ; and the lower, true, cords. The true vocal chords are elastic ligaments tensed by the adjacent vocalis muscle, and are covered with stratified squamous epithelium.

There are no glands in their lamina propria. 6 The epiglottis, too, has stratified squamous epithelium on its exposed tip and upper surface.3 Trachea l Flexible, extensible tube, with an always-patent lumen. 2 Mucosa as for the larynx, and the cilia sweep towards the pharynx, but the elastic fibres run longitudinally as a layer between mucosa and submucosa.

3 Supporting C-shaped pieces of hyaline cartilage are incomplete on their oesophageal side. 4 The gap in the C is crossed by trachealis smooth muscle and CT. 5 Outer adventitia is fibro-elastic CT. B LUNGSThe structure of the lungs reflects the way in which the air is moved: (a) the lungs are covered by a slippery membrane and are enclosed in another membrane, adherent to the inner chest wall, with a potential space between; (b) the lungs are stretched out against their considerable elasticity , so that this space remains only a potential one; (c) the larger conducting tubes of the lung need firm cartilages in their walls to prevent their collapsing during the inspiratory sucking in of air.l Bronchial tree serving the lungs l Primary bronchi branch to form the 2 intrapulmonary lobar bronchi, branching to form segmental bronchi, then lobular bronchioles.

After about 9-l2 generations of branching, bronchioles replace bronchi. 3 Terminal bronchioles lead to respiratory bronchioles, off which open the respiratory exchange units, and not just at the end, but along the bronchiole.

[For efficiency, the branching, tubular architecture of air conductance overlaps slightly the honeycomb architecture of gas exchange.] 4 Bronchi resemble the trachea in structure, except that the cartilage pieces in the wall have very irregular shapes, and the smooth muscle forms a nearly complete layer - muscularis mucosae - between the cartilages and the lumen.

5 Bronchioles are smaller than bronchi: .. they have no cartilages; .. their elastic fibres merge with those of the surrounding lung tissue; .. the epithelium changes to simple, low ciliated columnar with a few goblet cells; .. no mucous glands are present in the lamina propria, where the smooth muscle is relatively substantial.

6 Sharing the connective tissue of the branching bronchi are blood vessels, nerves and lymphatic vessels, entering or leaving at the hilum or lung root.

7 Hilar structures include arteries (bronchial and pulmonary), veins, lymphatics (from two systems), bronchi, lymph nodes, ganglia, nerves (to bronchial, bronchiolar, and vascular smooth muscles; and sensory), and adipose and other CT.

The carotid body-like glomus pulmonale in the pulmonary artery's adventitia is of uncertain function.2 Mucosa of the lower airway Cell types in the epithelium: (a) ciliated columnar cells, with lysosomes and some microvilli; (b) mucus-secreting goblet cells; (c) basal 'undifferentiated' cells to replace the specialized kinds; (d) Clara's non-ciliated bronchiolar secretory cells with granules and GER; (e) neuroendocrine cells ; (f) lymphocytes migrated from the lamina propria. A sheet of sticky mucus is moved by ciliary action over the mucosa to catch and remove particles - the mucociliary escalator . The basal lamina typically is thick. Muco-serous mixed glands, where present in the lamina propria, are small, compound tubular, and respond under nervous control to irritant stimuli, e.g., sm

3 At the end of the respiratory bronchiole are one or more long alveolar ducts. 4 Alveolar ducts can be viewed as being three to six atria , vestibules, leading to alveolar sacs, made up of varying numbers of alveoli. Processing distortions in lung slides often make the atria and sacs hard to make out. 5 One alveolus or cubicle shares an alveolar wall with the ones adjacent and backing on to it.

The wall is thus interalveolar and carries the many capillaries, whose blood is to receive oxygen and give up carbon dioxide. 6 Angiotensin converting enzyme in pulmonary capillaries cleaves angiotensin I to make it the potent angiotensin II.4 Interalveolar wall l Air side - continuous alveolar epithelium with: .. (a) type I pneumocytes /squamous cells; and .. (b) pneumocytes type II /septal or great alveolar cells, with prominent lipid cytosomes/ multilamellar bodies in their cytoplasm.

2 Surfactant is a stabilizing fluid film of lipids (90%) and proteins (10%), covering the epithelium and lowering surface tension. The principal surface-active agent is the lipid, dipalmitoyl phosphatidylcholine (DPPC). The type II cells synthesize this film, but also are the stem cell to replace themselves and Type I cells.

Cytosomes are stored surfactant. 3 Alveolar macrophages /dust cells lie free in the alveoli. 4 Alveolar epithelium lies on a basal lamina sometimes merging with, and sometimes separated from, the 5 basal lamina of a blood capillary, on which lies an 6 unfenestrated endothelium on the blood side.

7 Where the two basal laminae are separated, the space - zona diffusa - is taken by elastic and reticular fibres, fibroblasts, macrophages and other CT cells. 8 The pulmonary blood-air barrier can therefore be as thin as 300 nm, and has a very extensive area. 9 Communication between adjacent alveolar sacs is through holes in the wall - alveolar pores. l0 Basal laminae, fibres, and surfactant maintain the shape and patency of alveoli during respiration.5 Pleurae are fibro-elastic vascular membranes with mesothelial coverings.

From the visceral pleura, CT septa run in to subdivide the lung into lobules and carry lymphatic and venous vessels. C RESPIRATORY TRACTl Development l From an endodermal bulge on the foregut, which gives the trachea, then two buds for the bronchi and lungs.

2 Continued budding and branching, and enclosure of the hollow buds by mesenchyme, produce a system of cuboidal epithelium-lined tubules with surrounding differentiating CT and vessels. 3 Early development thus is analogous to that of a compound exocrine gland, until the later phase, when the pulmonary alveoli form.

Inadequately developed alveoli, with no surfactant, are a major hazard of premature birth. 4 Surfactant comprises lipids, and surfactant glycoproteins SP-A, -B, -C, & -D, which variously cause the lamellar material to become a monolayer, enhance the lowering of surface tension, stabilise the lipids, and modify host defences. 5 For the development of glands and the lung, complex mesenchymal-epithelial inductive (instructional) interactions occur, and recur during repair and tumour development.2 Respiratory protective mechanisms Secretion of entrapping mucus by goblet cells and mixed glands,which is swept pharynx-wards by the ciliary beating action.

Solitary lymphoid nodules and tonsils, and their lymphocyte progeny, for immune defence . Phagocytic alveolar macrophages /dust cells. Reflex coughing, sneezing, and constriction of bronchioles. Secretion of serous bacteriolytic materials, e.g., defensins and lysozyme.

Upper airway recovers water and heat, preventing too much loss in the expired air. Some protection is hazardous in that enzymes from WBCs can break down elastin; and activated lung macrophages stimulate fibroblasts to lay down movement-restricting collagen - an interstitial fibrosis. Various defects in the arms and microtubules of cilia (primary ciliary dyskinesia) can prevent proper clearance and cause recurrent lung infection. Affected men are often infertile from an accompanying paralysis of sperm. William A Beresford, Anatomy Department, School of Medicine, West Virginia University, Morgantown, WV 26506-9128, USA - - e-mail: -- wberesfo@wvu.edu -- wberesfo@hotmail.com -- beresfo@wvnvm.wvnet.edu -- fax: 304-293-8159

wer Tissues that make up the lungs include bronchioles, epithelial cells, smooth muscle cells and alveoli, according to Centre of the Cell. Many of the lungs' tissues consist of several different cell types. Continue Reading

What Tissues Make up the Lungs?

Science Human Anatomy Organs Q: What Tissues Make up the Lungs? A: Quick Ans

Keep Learning What Is the Function of the Bronchioles? What Happens in the Alveoli? Alveoli Serve What Function in the Lungs? Full Answer The lungs are located in the thoracic cavity of the body, and they take up most of the space in that area, according to Inner Body.

The lungs are large, spongy organs that are surrounded by a double layer of serous membranes. The outer layer of the serous membrane is called the parietal pleura, and the inner layer, or visceral pleura, is the section that covers the lung surface. The pleural cavity, or hollow space within the lungs, is the part of the organ that expands when a person inhales.

If the inner surface of the lungs were to be stretched out and laid flat, it would be approximately the size of half a tennis court. The lungs are an extremely important part of a life cycle. The lungs take in oxygen, which is necessary for survival, and they rid the body of dangerous levels of carbon dioxide.

The bronchioles and the alveoli work together to help keep air moving through the body, according to Centre of the Cell. Learn more about Organs Sources: centreofthecell.org innerbody.com Related Questions Q: What Is the Function of a Respiratory Membrane?

A: The respiratory membrane allows gases to be exchanged between the pulmonary capillaries, or blood vessels, and the respiratory units of the lungs, which co... Full Answer >Filed Under: Organs Q: Explain the Process of Gas Exchange in the Lungs?

A: Gas exchange in the lungs allows oxygen to diffuse through the small air sacks or alveoli at the end of one's bronchial tubes into the blood, and it allows... Full Answer >Filed Under: Organs Q: Why Is the Heart Considered a Double Pump?

A: The heart is a single organ, but it functions as a double pump sending oxygen-depleted blood to the lungs to pick-up oxygen and unload carbon dioxide, whil... Full Answer >Filed Under: Organs Q: What Is the Main Function of the Heart?

A: The main function of the heart is to pump blood to the lungs to be saturated with oxygen, and then pump it out into the body to supply the cells with oxyge... Full Answer >Filed Under: Organs You May Also Like Q: What Organ Is Below Your Right Breast? Q: What Are the Dangers of a Horseshoe Kidney? Q: What Are Signs of Hardening of the Lungs? Q: How Far Can the Human Eye See? Q: How Is a Kidney Transplant Done? Q: What Side Is Your Gallbladder On?

The main function of the bronchi and bronchioles is to carry air from the trachea into the lungs. Smooth muscle tissue in their walls helps to regulate airflow into the lungs. When greater volumes of air are required by the body, such as during exercise, the smooth muscle relaxes to dilate the bronchi and bronchioles.

Respiratory System

Click To View Large Image Continued From Above... act as the functional units of the respiratory system by passing oxygen into the body and carbon dioxide out of the body. Finally, the muscles of respiration, including the diaphragm and intercostal muscles, work together to act as a pump, pushing air into and out of the lungs during breathing.

Anatomy of the Respiratory System Nose and Nasal Cavity The nose and nasal cavity form the main external opening for the respiratory system and are the first section of the body’s airway—the respiratory tract through which air moves.

The nose is a structure of the face made of cartilage, bone, muscle, and skin that supports and protects the anterior portion of the nasal cavity. The nasal cavity is a hollow space within the nose and skull that is lined with hairs and mucus membrane. The function of the nasal cavity is to warm, moisturize, and filter air entering the body before it reaches the lungs. Hairs and mucus lining the nasal cavity help to trap dust, mold, pollen and other environmental contaminants before they can reach the inner portions of the body.

Air exiting the body through the nose returns moisture and heat to the nasal cavity before being exhaled into the environment. Mouth The mouth, also known as the oral cavity, is the secondary external opening for the respiratory tract.

Most normal breathing takes place through the nasal cavity, but the oral cavity can be used to supplement or replace the nasal cavity’s functions when needed. Because the pathway of air entering the body from the mouth is shorter than the pathway for air entering from the nose, the mouth does not warm and moisturize the air entering the lungs as well as the nose performs this function.

The mouth also lacks the hairs and sticky mucus that filter air passing through the nasal cavity. The one advantage of breathing through the mouth is that its shorter distance and larger diameter allows more air to quickly enter the body. Pharynx The pharynx, also known as the throat, is a muscular funnel that extends from the posterior end of the nasal cavity to the superior end of the esophagus and larynx.

The pharynx is divided into 3 regions: the nasopharynx, oropharynx, and laryngopharynx. The nasopharynx is the superior region of the pharynx found in the posterior of the nasal cavity. Inhaled air from the nasal cavity passes into the nasopharynx and descends through the oropharynx, located in the posterior of the oral cavity. Air inhaled through the oral cavity enters the pharynx at the oropharynx. The inhaled air then descends into the laryngopharynx, where it is diverted into the opening of the larynx by the epiglottis.

The epiglottis is a flap of elastic cartilage that acts as a switch between the trachea and the esophagus. Because the pharynx is also used to swallow food, the epiglottis ensures that air passes into the trachea by covering the opening to the esophagus. During the process of swallowing, the epiglottis moves to cover the trachea to ensure that food enters the esophagus and to prevent choking.

Larynx The larynx, also known as the voice box, is a short section of the airway that connects the laryngopharynx and the trachea.

The larynx is located in the anterior portion of the neck, just inferior to the hyoid bone and superior to the trachea. Several cartilage structures make up the larynx and give it its structure. The epiglottis is one of the cartilage pieces of the larynx and serves as the cover of the larynx during swallowing.

Inferior to the epiglottis is the thyroid cartilage, which is often referred to as the Adam’s apple as it is most commonly enlarged and visible in adult males. The thyroid holds open the anterior end of the larynx and protects the vocal folds. Inferior to the thyroid cartilage is the ring-shaped cricoid cartilage which holds the larynx open and supports its posterior end.

In addition to cartilage, the larynx contains special structures known as vocal folds, which allow the body to produce the sounds of speech and singing. The vocal folds are folds of mucous membrane that vibrate to produce vocal sounds. The tension and vibration speed of the vocal folds can be changed to change the pitch that they produce.

Trachea The trachea, or windpipe, is a 5-inch long tube made of C-shaped hyaline cartilage rings lined with pseudostratified ciliated columnar epithelium. The trachea connects the larynx to the bronchi and allows air to pass through the neck and into the thorax.

The rings of cartilage making up the trachea allow it to remain open to air at all times. The open end of the cartilage rings faces posteriorly toward the esophagus, allowing the esophagus to expand into the space occupied by the trachea to accommodate masses of food moving through the esophagus.

The main function of the trachea is to provide a clear airway for air to enter and exit the lungs. In addition, the epithelium lining the trachea produces mucus that traps dust and other contaminants and prevents it from reaching the lungs.

Cilia on the surface of the epithelial cells move the mucus superiorly toward the pharynx where it can be swallowed and digested in the gastrointestinal tract. Bronchi and Bronchioles At the inferior end of the trachea, the airway splits into left and right branches known as the primary bronchi.

The left and right bronchi run into each lung before branching off into smaller secondary bronchi. The secondary bronchi carry air into the lobes of the lungs—2 in the left lung and 3 in the right lung. The secondary bronchi in turn split into many smaller tertiary bronchi within each lobe. The tertiary bronchi split into many smaller bronchioles that spread throughout the lungs.

Each bronchiole further splits into many smaller branches less than a millimeter in diameter called terminal bronchioles.

Finally, the millions of tiny terminal bronchioles conduct air to the alveoli of the lungs. As the airway splits into the tree-like branches of the bronchi and bronchioles, the structure of the walls of the airway begins to change. The primary bronchi contain many C-shaped cartilage rings that firmly hold the airway open and give the bronchi a cross-sectional shape like a flattened circle or a letter D. As the bronchi branch into secondary and tertiary bronchi, the cartilage becomes more widely spaced and more smooth muscle and elastin protein is found in the walls.

The bronchioles differ from the structure of the bronchi in that they do not contain any cartilage at all. The presence of smooth muscles and elastin allow the smaller bronchi and bronchioles to be more flexible and contractile.

The main function of the bronchi and bronchioles is to carry air from the trachea into the lungs. Smooth muscle tissue in their walls helps to regulate airflow into the lungs. When greater volumes of air are required by the body, such as during exercise, the smooth muscle relaxes to dilate the bronchi and bronchioles.

The dilated airway provides less resistance to airflow and allows more air to pass into and out of the lungs. The smooth muscle fibers are able to contract during rest to prevent hyperventilation. The bronchi and bronchioles also use the mucus and cilia of their epithelial lining to trap and move dust and other contaminants away from the lungs.

Lungs The lungs are a pair of large, spongy organs found in the thorax lateral to the heart and superior to the diaphragm. Each lung is surrounded by a pleural membrane that provides the lung with space to expand as well as a negative pressure space relative to the body’s exterior.

The negative pressure allows the lungs to passively fill with air as they relax. The left and right lungs are slightly different in size and shape due to the heart pointing to the left side of the body. The left lung is therefore slightly smaller than the right lung and is made up of 2 lobes while the right lung has 3 lobes.

The interior of the lungs is made up of spongy tissues containing many capillaries and around 30 million tiny sacs known as alveoli. The alveoli are cup-shaped structures found at the end of the terminal bronchioles and surrounded by capillaries.

The alveoli are lined with thin simple squamous epithelium that allows air entering the alveoli to exchange its gases with the blood passing through the capillaries. Muscles of Respiration Surrounding the lungs are sets of muscles that are able to cause air to be inhaled or exhaled from the lungs. The principal muscle of respiration in the human body is the diaphragm, a thin sheet of skeletal muscle that forms the floor of the thorax.

When the diaphragm contracts, it moves inferiorly a few inches into the abdominal cavity, expanding the space within the thoracic cavity and pulling air into the lungs.

Relaxation of the diaphragm allows air to flow back out the lungs during exhalation. Between the ribs are many small intercostal muscles that assist the diaphragm with expanding and compressing the lungs. These muscles are divided into 2 groups: the internal intercostal muscles and the external intercostal muscles.

The internal intercostal muscles are the deeper set of muscles and depress the ribs to compress the thoracic cavity and force air to be exhaled from the lungs. The external intercostals are found superficial to the internal intercostals and function to elevate the ribs, expanding the volume of the thoracic cavity and causing air to be inhaled into the lungs.

Physiology of the Respiratory System Pulmonary Ventilation Pulmonary ventilation is the process of moving air into and out of the lungs to facilitate gas exchange. The respiratory system uses both a negative pressure system and the contraction of muscles to achieve pulmonary ventilation. The negative pressure system of the respiratory system involves the establishment of a negative pressure gradient between the alveoli and the external atmosphere.

The pleural membrane seals the lungs and maintains the lungs at a pressure slightly below that of the atmosphere when the lungs are at rest. This results in air following the pressure gradient and passively filling the lungs at rest. As the lungs fill with air, the pressure within the lungs rises until it matches the atmospheric pressure.

At this point, more air can be inhaled by the contraction of the diaphragm and the external intercostal muscles, increasing the volume of the thorax and reducing the pressure of the lungs below that of the atmosphere again. To exhale air, the diaphragm and external intercostal muscles relax while the internal intercostal muscles contract to reduce the volume of the thorax and increase the pressure within the thoracic cavity.

The pressure gradient is now reversed, resulting in the exhalation of air until the pressures inside the lungs and outside of the body are equal.

At this point, the elastic nature of the lungs causes them to recoil back to their resting volume, restoring the negative pressure gradient present during inhalation. External Respiration External respiration is the exchange of gases between the air filling the alveoli and the blood in the capillaries surrounding the walls of the alveoli.

Air entering the lungs from the atmosphere has a higher partial pressure of oxygen and a lower partial pressure of carbon dioxide than does the blood in the capillaries.

The difference in partial pressures causes the gases to diffuse passively along their pressure gradients from high to low pressure through the simple squamous epithelium lining of the alveoli. The net result of external respiration is the movement of oxygen from the air into the blood and the movement of carbon dioxide from the blood into the air. The oxygen can then be transported to the body’s tissues while carbon dioxide is released into the atmosphere during exhalation.

Internal Respiration Internal respiration is the exchange of gases between the blood in capillaries and the tissues of the body. Capillary blood has a higher partial pressure of oxygen and a lower partial pressure of carbon dioxide than the tissues through which it passes.

The difference in partial pressures leads to the diffusion of gases along their pressure gradients from high to low pressure through the endothelium lining of the capillaries. The net result of internal respiration is the diffusion of oxygen into the tissues and the diffusion of carbon dioxide into the blood.

Transportation of Gases The 2 major respiratory gases, oxygen and carbon dioxide, are transported through the body in the blood. Blood plasma has the ability to transport some dissolved oxygen and carbon dioxide, but most of the gases transported in the blood are bonded to transport molecules.

Hemoglobin is an important transport molecule found in red blood cells that carries almost 99% of the oxygen in the blood. Hemoglobin can also carry a small amount of carbon dioxide from the tissues back to the lungs. However, the vast majority of carbon dioxide is carried in the plasma as bicarbonate ion.

When the partial pressure of carbon dioxide is high in the tissues, the enzyme carbonic anhydrase catalyzes a reaction between carbon dioxide and water to form carbonic acid. Carbonic acid then dissociates into hydrogen ion and bicarbonate ion. When the partial pressure of carbon dioxide is low in the lungs, the reactions reverse and carbon dioxide is liberated into the lungs to be exhaled.

Homeostatic Control of Respiration Under normal resting conditions, the body maintains a quiet breathing rate and depth called eupnea. Eupnea is maintained until the body’s demand for oxygen and production of carbon dioxide rises due to greater exertion. Autonomic chemoreceptors in the body monitor the partial pressures of oxygen and carbon dioxide in the blood and send signals to the respiratory center of the brain stem. The respiratory center then adjusts the rate and depth of breathing to return the blood to its normal levels of gas partial pressures.

Health Issues Affecting the Respiratory System When something impairs our ability to exchange carbon dioxide for oxygen, this is obviously a serious problem. Many health problems can cause respiratory problems, from allergies and asthma to pneumonia and lung cancer.

The causes of these issues are just as varied—among them, infection (bacterial or viral), environmental exposure (pollution or cigarette smoke, for instance), genetic inheritance or a combination of factors. Sometimes the onset is so gradual, we don’t seek medical attention until the condition has advanced. Sometimes, as with the genetic disorder called alpha-1 antitrypsin deficiency (A1AD), symptoms gradually set in and are often under-diagnosed or misdiagnosed. DNA health testing can screen you for genetic risk of A1AD. Prepared by Tim Taylor, Anatomy and Physiology Instructor

The cartilage and mucous membrane of the primary bronchi are similar to that in the trachea. As the branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the smallest bronchioles. As the cartilage decreases, the amount of smooth muscle increases.

Bronchi, Bronchial Tree, & Lungs

Bronchi, Bronchial Tree, & Lungs Bronchi and Bronchial Tree In the mediastinum, at the level of the fifth thoracic vertebra, the trachea divides into the right and left primary bronchi. The bronchi branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli.

The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium. The alveolar ducts and alveoli consist primarily of simple squamous epithelium, which permits rapid diffusion of oxygen and carbon dioxide.

Exchange of gases between the air in the lungs and the blood in the capillaries occurs across the walls of the alveolar ducts and alveoli.

Lungs The two lungs, which contain all the components of the bronchial tree beyond the primary bronchi, occupy most of the space in the thoracic cavity. The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue.

They are separated from each other by the mediastinum, which contains the heart. The only point of attachment for each lung is at the hilum, or root, on the medial side.

This is where the bronchi, blood vessels, lymphatics, and nerves enter the lungs. The right lung is shorter, broader, and has a greater volume than the left lung. It is divided into three lobes and each lobe is supplied by one of the secondary bronchi. The left lung is longer and narrower than the right lung. It has an indentation, called the cardiac notch, on its medial surface for the apex of the heart. The left lung has two lobes.

Each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung. At the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax. The small space between the visceral and parietal pleurae is the pleural cavity. It contains a thin film of serous fluid that is produced by the pleura.

The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the lungs inflate and deflate.« Previous (Larynx & Trachea) Next (Review) »

.6. Trace the pathway of air from the trachea to the respiratory zone. Trachea, to primary bronchi, to secondary bronchi, to tertiary bronchi, to smaller bronchi, to bronchioles, to terminal bronchioles, to respiratory zone.7. Describe the difference between bronchi and bronchioles in terms of smooth muscle and cartilage. Bronchi have rings of cartilage that keep them open.

"Name Anatomy Review1. What is the main function of the respiratory system? To bring oxygen into the body and eliminate carbon dioxide from the body.2. Trace the pathway of air from the outside of the body into the body. Air enters the nose through the external nares.

Then the air passes through the nasal cavity, pharynx, larynx, trachea, primary bronchus, and into the lungs.3-4. Describe the location of the visceral and parietal pleura. Visceral pleura covers the surface of the lungs. Parietal lines the mediastinum, the diaphragm, and the thoracic wall.5. What is the function of pleural fluid?

Assists in breathing movements by acting as a lubricant

Bronchioles have no cartilage, but they do have smooth muscle in their walls.8. What is the function of the smooth muscle of the bronchioles? To allow airflow regulation by altering the diameter of the bronchioles.9. Where is the conducting zone and what is its function?

The conducting zone is the airway from the nasal cavity through the terminal bronchioles. Its function is to moisten, warm, and filter the air.10. Where are three places alveoli are found? (1) In respiratory bronchioles where they are scattered in the walls.

(2) In alveolar ducts, which are completely lined by alveoli. (3) In alveolar sacs, where they are found in clusters.11. What are the names of the blood vessels that carry blood to the lungs? The pulmonary arteries and branches of the pulmonary arteries.12. What are the names of the blood vessels that carry blood away from the lungs? The pulmonary veins and branches of the pulmonary veins.13. Which contain blood that is higher in oxygen, the pulmonary arteries or the pulmonary veins? The pulmonary veins.14.

Where are the pulmonary capillaries found within the lung? They surround each alveolus.15. What three cell types are found within alveoli? (1) simple squamous epithelium, (2) alveolar macrophages, (3) surfactant-secreting cells16. What is the function of the alveolar macrophages, or dust cells, within alveoli? They creep along the inner surface of the alveoli, removing debris and microbes.17. What is the function of the surfactant-secreting, or Type II cells, within alveoli?

They secrete surfactant.18. What is present on the inside surface of alveoli? Alveolar fluid, which is composed of water and surfactant.19. What would happen if there were no surfactant in alveolar fluid? The alveoli would collapse due to the surface tension of the water.20.

Why is there no interstitial fluid in between the two layers of simple squamous epithelium in the respiratory membrane? Because pulmonary blood pressure is so low that little fluid filters out of the capillaries into the interstitial space.21.

What two important gases diffuse across the respiratory membrane? In which direction does each gas flow? Oxygen gas diffuses from the alveoli to the pulmonary capillaries. Carbon dioxide diffuses from the pulmonary capillaries to the alveoli. Control of Respiration22. What controls the basic rhythm of breathing? Respiratory centers located in the brainstem.23.

What monitors changes in arterial P CO 2, P O 2and p H? Sensory receptors called chemoreceptors.24. Explain how the inspiratory center initiates inspiration. The inspiratory center sends nerve impulses along the phrenic nerve to the diaphragm and along the intercostal nerves to the external intercostal muscles which continue for a period of about 2 seconds.

This stimulates the inspiratory muscles to contract, initiating inspiration.25. Explain how the inspiratory center initiates expiration The inspiratory center causes the phrenic nerve to stop firing for about 3 seconds, which allows the muscles of respiration to relax.

The elastic recoil of the lungs and chest wall leads to expiration.26-35. In each of these blanks, put ""increase (s)"" or ""decrease (s)"": If the arterial P CO 2increases, there is a (an) a. __ increase __ in the P CO 2in the fourth ventricle. This causes a (an) b. __ increase ___ in hydrogen ions in the cerebrospinal fluid, which c. _ decreases _ the p H of the cerebrospinal fluid.

The hydrogen ions stimulate the central chemoreceptors to d. _ increase __ their rate of firing, which e. _ increases _ the nerve impulses to the respiratory centers.

This f. _ increases _ the rate of nerve impulses to the respiratory muscles, resulting in a (an) g. _ increase _ in breathing rate and depth. As a result, there is a (an) h. __ increase __ in carbon dioxide exhalation which i. _ decreases _ the blood P CO 2to normal levels.36. Do peripheral chemoreceptors directly respond to changes in the arterial blood, venous blood, or cerebrospinal fluid? Arterial blood37-41. In each of these blanks, put ""increase (s)"" or ""decrease (s)"": An increase in carbon dioxide levels in the arterial blood result in a (an) a.

__ decrease __ in blood p H. There is a (an) b. _ increase __ in the rate of firing of the peripheral chemoreceptors, which c, __ increases __ the rate of respiration.

As a result there is a (an) d. __ increase __ in carbon dioxide exhalation, which drives the chemical reaction to the left and e. _ decreases __ P CO 2and p H returns to normal levels.42-50.

In each of these blanks, put ""increase (s)"" or ""decrease (s)"": The peripheral chemoreceptors also respond to acids such as lactic acid, which a. _ increases _ during strenuous exercise. The lactic acid enters the blood and b. _ increases _ the concentration of hydrogen ions which c. _ decreases _ the p H which d. _ increases _ the firing rate of the peripheral chemoreceptors.

There is a (an) e. __ increase _ in nerve impulses to the respiratory centers, which f. _ increases _ the breathing rate and depth.

There is a (an) g. _ increases _ in carbon dioxide is exhalation which h. __ decreases __ the P CO 2 in blood, driving the chemical reaction to the left, and i. _ decreases _ hydrogen ion levels.51. What is the Hering-Breuer reflex? Stretch receptors in the visceral pleura and large airways send inhibitory signals to the inspiratory center during very deep inspirations, protecting against excessive stretching of the lungs.52.

Do changes in P CO 2and P O 2play a significant role in stimulating increased ventilation due to exercise? No they do not play a significant role.53. What are the factors that stimulate increased ventilation during exercise? Learned responses, Neural input from the motor cortex, Receptors in muscles and joints, Increased body temperature, Circulating epinephrine and norepinephrine and p H changes due to lactic acid.

Pulmonary Ventilation54. How is the volume of the thoracic cavity changed? By muscle contraction and relaxation.55.

What two muscles contract during quiet inspiration? What is the effect of their contraction? The diaphragm and the external intercostals. As a result the thoracic cavity enlarges in all dimensions.56. What happens to pressure when we increase the volume within the thoracic cavity and the lungs? Pressure decreases.57. Explain what happens in quiet expiration. The diaphragm and the external intercostal muscles relax, and the elastic lungs and thoracic wall recoil inward.58.

What effect does quiet expiration have on the volume of the thoracic cavity? How does this effect the pressure within the cavity? The volume is decreased and therefore the pressure increases within the thoracic cavity.59-61. What three factors cause the intrapleural pressure to be less than intrapulmonary (alveolar) pressure?

(1) The surface tension of the alveolar fluid. (2) The elasticity of the lungs. (3) The elasticity of the thoracic wall.62. Why does a lung collapse if you cut into the pleural cavity? Because the pressure of the intrapleural cavity becomes equal to atmospheric pressure. There is no longer less pressure in the intrapleural cavity compared to within the alveoli so the lung collapses.63. If a pneumothorax occurs in one lung, why doesn't it also occur in the other lung? Each lung has its own pleural cavity and pleural membranes so that changes in the intrapleural pressure of one lung do not affect the other lung.64. Does histamine constrict or dilate bronchioles? Constrict65. Does epinephrine constrict or dilate bronchioles? Dilate66. What two factors is lung compliance dependent upon? (1) The stretchability of the elastic fibers within the lungs. (2) The surface tension within the alveoli. "

Bronchioles are small airways that branch off the bronchi in thelungs. Their role is to transport air to the alveoli where gasexchange can take place.

What is bronchioles?

Ktimmons 87 Contributions What is bronchioles? Answer . The bronchioles are the first airway branches that no longer contain cartilage.

They are branches of the bronchi, and are smaller than one millimeter in diameter. …Dodi Tov 275,915 Contributions Old ladies are dangerous. Always remember that. I'm an old lady. Follow the logic. Where is the location of bronchioles? Answer . in the lungs. Gaines Fox 66,077 Contributions What is the structure of bronchioles? Air enters the body through the nostrils or the mouth, passing down the throat to the larynx, and then to the trachea.

The trachea divides into two branches in the chest cavit …Jazz M 28,354 Contributions A veterinarian with a love of animals, history and tea. What is the function of the bronchioles?

The areas of gas exchang …What is the function of bronchioles? The function of the bronchioles is to store the alveolis in. ae Song63 10 Contributions What is a bronchiole dilator? It is medication taken by an inhauler or hand held nebulizer which helps to open up the bronchi to help people who are having a difficult time with breathing.

Most frequently …Can adults get bronchiolitis? THE ANSWER IS A DEFINITE YES, YES AND YES. ADULTS MISTAKE IT FOR OTHER ILLNESSES.

I had no idea what Bronchialitis/Bronchiolitis was until I ended up in hospital and was told …Out of Here 838,246 Contributions What is the function of the bronchiole? The bronchi, or bronchus is where the air entering the lungs are sent to each lung. The bronchioles are smaller airways that send the air on to the inside walls of the lungs w …Never Shout Never88 6 Contributions What is the job of the bronchiole?

The brochiole's function is to allow oxygen to pass into the aveoli (air sacks covered in capillaries) where the oxygen can then enter your blood stream.

Jazz M 28,354 Contributions A veterinarian with a love of animals, history and tea. Do bronchioles have cartilage?

No, bronchioles (except in the whale) do not contain cartilage. The bronchioles in whales contain cartilage in order to prevent them from collapsing before other parts of t …What are bronchiole? Tiny air sacks that hold portions of air. What do the bronchioles connect? The Bronchioles connect the brochi and the alveoli

ll A cuboidal epithelial cell found in the lining of the terminal and the respiratory bronchioles of thelungs. Clara cells are nonciliated, and they secrete surfactant, like the type II alveolar epithelial cellsfound deeper in the bronchial tree.

progenitor cell

"progenitor cell (redirected from Progenitor cells) Also found in: Dictionary, Encyclopedia. Related to Progenitor cells: Stem cellsprogenitor cellunipotential hemopoietic stem cell located in bone marrow; give rise to a single cell line (e.g.,erythrocytes); resembling lymphocytes, considered part of null cell (q.v.) population. See also: stem cell, null cells. Farlex Partner Medical Dictionary © Farlex 2012progenitor celln.

A cell that originates from a stem cell and differentiates into a more specialized cell. The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.cell (sel) [L. cella, a chamber]GENERALIZED HUMAN CELL AND ORGANELLESThe basic unit of life.

A cell is a group of self-sustaining biochemical reactions that areisolated from the environment by a selectivelypermeable lipid membrane. Among the keyreactions are those that maintain a stableintracellular concentration of ions; formammalian cells, typical internal concentrationsinclude 140 m M K+, 5-15 m M Na+, 5-15 m M Cl-, and a p H of 7.2, which can be significantlydifferent from their concentrations outside thecell.

Other key reactions move molecules andmolecular complexes within the cell, sometimeschanging the cell's shape. These reactions,along with many others, require energy, and thegeneration of energy by breaking apartpreexisting hydrocarbon molecules (""food"") is the job of glycolysis and other characteristicintracellular metabolic reactions.

See:glycolysis; metabolism; mitochondrion. Structure Intracellular chemical reactions are controlled by enzymes that are organized in stable molecularcomplexes called organelles. The polymer-based organelles include centrioles and thecytoskeleton; nucleic acid-based organellesinclude ribosomes; and membrane-enclosedorganelles include the nucleus, endoplasmicreticula, Golgi complexes, lysosomes,peroxisomes, mitochondria, and storage andtransport vesicles.

See: illustration Individualmammalian cells are usually microscopic,typically ranging from 5 µm to 50 µm in diameter.

In humans, lymphocytes are smallcells (~6 µm in diameter), columnar epithelialcells (10 µm x 20 µm) are medium-size cells,and mature ova (120-150 µm) are some of thelargest cells. Cell Division In mammals, all new cells arise from existingcells through cell division, and an animal'sgrowth results largely from increases in thenumber of its cells, most of which differentiateinto specialized cell types to form the body'svarious tissues.

Cell division involves two majorprocesses: karyokinesis, the division of thenucleus, and cytokinesis, the division of theremainder of the cell. When generating somaticdaughter cells, karyokinesis uses a processcalled mitosis, which produces daughter cellswith a full complement of chromosomes.

Whengenerating germ cells, karyokinesis includes a process called meiosis, which producesdaughter cells with half the normal number of chromosomes. See: meiosis and mitosis forillus. A cell Alpha cell of the pancreas.accessory cell A monocyte or macrophage that participates in the immune response. See: antigen-presenting cell; macrophageacidophilic cell Acidophil.acinar cell A cell present in the acinus of an acinous gland, e.g., of the pancreas.adipose cell Adipocyte..adult stem cell A precursor cell that can also give rise to identical precursor cells: daughters of a stem cell candevelop into a terminally-differentiated cell type or they can remain a stem cell.

Adult stem cells arefound in many tissues, such as bone marrow, brain, retina, skin, intestines, liver, testis, andpancreas.

Synonym: somatic stem cell See: embryonic stem celladventitial cell A macrophage along a blood vessel, together with perivascular undifferentiated cells associated withit.air cell An air-filled sinus cavity in a bone.alpha cell1. An enteroendocrine cell that produces glucagon and is found in the pancreatic islets. Synonym: A cell2.

An acidophil of the adenohypophysis (anterior pituitary gland).alveolar cell1. In the lung, either of two types of epithelial cells lining the alveoli. Type I cells are simplethin squamous epithelial cells. Type II cells secrete pulmonary surfactant.

Type II cells aresmaller and more numerous than Type I cells.2. In the mammary glands, the milk-secreting epithelial cells, which are activated duringlactation.amacrine cell A modified nerve cell in the retina that has dendrites but no axon. See: neuronameloblast cell Ameloblast.anterior horn cell A somatic motor neuron that has its cell body in the ventral (anterior) horn of the gray matter of thespinal cord; its axon passes out through a ventral root and innervates skeletal muscle.antigen-presenting cell Abbreviation: APCA cell that breaks down antigens and displays their fragments on surface receptors next to majorhistocompatibility complex molecules.

This presentation is necessary for some T lymphocytes thatare unable to recognize soluble antigens.

Macrophages are the primary antigen-presenting cells, but B cells and dendritic cells also can act as APCs. See: T cell; macrophage processing cell APUDThe abbreviated name for an 'amine precursor uptake and decarboxylation cell'. These cells are theconstituents of a diffuse neuroendocrine system and all have metabolic pathways that make andutilize serotonin (5-HT).

APUD cells include chromaffin cells, enterochromaffin cells, and SIF cells as well as certain cells found in the parathyroid gland, thyroid gland, pituitary gland, hypothalamus,and placenta.argentaffin cell A cell in the epithelium of the stomach, intestines, and appendix that secretes serotonin.astroglial cell Astrocyte.atypical glandular cells Abbreviation: AGCAn abnormal finding on a Pap test.

This classification is divided into “favor neoplasia” or “nototherwise specified (NOS).” NOS is subdivided into endocervical or endometrial origin. Atypicalendocervical cells are important because of their risk for significant disease. Synonym: atypical glandular cells of undetermined significanceatypical glandular cells of undetermined significance Abbreviation: AGUSAtypical glandular cells.

B cell1. A lymphocyte that synthesizes and secretes antibodies. B lymphocytes originate anddifferentiate in the bone marrow and then populate the spleen, lymph nodes, and otherlymphoid tissues. When exposed to an antigen, a B cell divides to form (a) plasma cells,which produce antigen-specific antibodies, and (b) a lesser number of memory B cells, whichcan quickly differentiate into plasma cells upon a second exposure to the original antigen.

Antibody production is a key part of the humoral immune response of adaptive immunity. Thehumoral immune response is effective against bacteria, viruses, and other pathogens, andprovides the rationale for vaccination. Synonym: B lymphocyte See:; T cell;2. Pancreatic beta cell.band cell The developing leukocyte at a stage at which the nucleus is not segmented.basal cell1. A rounded or cuboidal epithelial stem cell found in the bottom layer of pseudostratifiedepithelia, such as the epidermis and the lining of the airways of the lung.2.

Either of two types of cell found in the bottom layer of the olfactory epithelium; one type is a flattened ""basal cell proper"", and the other is a rounded stem cell called a globose cell.3. A rounded stem cell found in the taste buds and a progenitor of the specialized tastereceptor cells.basket cell1.

Myoepithelial cell.2. One of the nonspiny granule cells found in the cerebral cortex.3. One of the small interneurons found in the outermost layer of the cerebellar cortex alongwith stellate cells.basophilic cell Basophil.beta cell1. Any of the insulin-secreting cells of the pancreas that constitute the bulk of the islets of Langerhans. Synonym: B cell2. A basophil cell of the adenohypophysis (anterior pituitary gland). Betz cell See: Betz cellsbipolar cell Bipolar neuron.blast cell1.

A precursor cell for a specific cell type.2. An immature cell of a specific type.blood cell Any cell normally found circulating in the blood stream. Blood cells include red cells and white cells;red cells generally remain inside blood vessels, while white cells can also more into the tissuesoutside the blood vessel walls.

See: blood for illus.bone cell An osteoblast, osteoclast, or osteocyte.bone marrow cell Marrow cell.brush cell An epithelial cell found sparsely in the lining of the bronchial tree.

The cell's surface has long stiffmicrovilli, and the cell has the appearance of an absorptive cell.burr cell An erythrocyte with 10 to 30 spicules distributed over the surface of the cell, as seen in heartdisease, stomach cancer, kidney disease, and dehydration.

Synonym: echinocytecancer cell A cell present in a neoplasm and differentiated from normal tissue cells because of its degree of anaplasia, irregularity of shape, nuclear size, changes in the structure of the nucleus andcytoplasm, increased number of mitoses, and ability to metastasize.capsule cell Satellite cell.cartilage cell Chondrocyte.castration cell An enlarged and vacuolated basophil cell seen in the pituitary in gonadal insufficiency or followingcastration. CD3 cell T cell. CD4 cell Helper T cell. CD8 cell A suppressor T cell, e.g., a cytotoxic T cell.

CD 34+ cell A cell with the CD34 protein on its surface membrane. Some CD34 cells that are hemopoietic stemcells can be separated out from peripheral blood.cementoblast cell Cementoblast.cementocyte cell Any of the cells trapped within cementum that maintain cementum as a living calcified tissue by their metabolic activity.centroacinar cell A duct cell of the pancreas more or less invaginated into the lumen of an acinus.chalice cell Goblet cell.chemoreceptor cell Chemoreceptor.chief cell1. Any of the cells of the parathyroid gland that secretes the parathyroid hormone.2. Any of the cells of the gastric glands that secretes pepsinogen.chromaffin cell A cell that produces, stores, and secretes catecholamines (dopamine and norepinephrine). Chromaffin cells are found in the medulla of the adrenal glands and in small clusters in thesympathetic ganglia.chromophobe cell Chromophobe. Clara ce

ll A cuboidal epithelial cell found in the lining of the terminal and the respiratory bronchioles of thelungs. Clara cells are nonciliated, and they secrete surfactant, like the type II alveolar epithelial cellsfound deeper in the bronchial tree.

cleavage cell Blastomere.clue cell A vaginal epithelial cell, thickly coated with coccobacillary organisms. Clue cells are a hallmark of bacterial vaginosis.columnar cell An epithelial cell with height greater than its width.columnar epithelial cell Columnar cell.cone cell A cell in the retina whose scleral end forms a cone that serves as a light receptor.

Vision in brightlight, color vision, and acute vision depend on the function of the cones. See: rod cellcontrasuppressor cell A T cell that inhibits the activity of suppressor T cells.

Although a contrasuppressor cell shares thisfunctional capability with T helper cells, it is distinguished from other CD4+ cells by its other cellsurface markers and the unique group of cytokines it produces.cortical cell A cell in the cortex of an organ, e.g., a neuron in the cerebral cortex.corticotroph cell Corticotroph.cuboid cell A cell – usually epithelial – with a height about equal to its width and depth.cytotoxic cell Cytotoxic T cell.cytotoxic T cell A CD8+ T lymphocyte that can destroy microorganisms directly through the release of perforin andproteolytic enzymes.

These cells are particularly important in the defense against viruses, rejection of allografts, and, possibly, new malignant cells. Synonym: CD8 cell; cytotoxic cel; killer T cell D cell An enteroendocrine cell that produces somatostatin and is found in the pancreatic islets, stomach,and small intestine. Synonym: delta cell; somatostatin celldaughter cell A cell formed by cell division.decoy cell A cell found in the urine with inclusion bodies in its nucleus.

It indicates infection with BK virus in renal transplant recipients.delta cell Pancreatic D cell.dendritic cell One type of antigen-presenting cell that helps T cells respond to foreign antigens. Dendritic cells arefound in epithelial tissues and include the Langerhans' cells of the skin and the interdigitating cells in lymph nodes; they also circulate in the blood.

Downey cell See: Downey celldust cell A macrophage that migrates into the lumen of lung aveoli and ingests debris, particles of airpollution, and pathogens to keep the airspaces clear. EC cell1. An embryonal carcinoma cell, which is a cultured cell line.2. An enterochromaffin cell that secretes substance P and is found in the stomach and smallintestine.effector cell A cell that carries out the final response or function of a particular process.

The main effector cells of the immune system, for example, are activated lymphocytes and phagocytes—the cells involved in destroying pathogens and removing them from the body. See: leukocyteembryonic stem cell Abbreviation: ES cell A cell from the inner cell mass of the blastocyst (the 3-5 day old mammalian embryo) that can giverise to all the somatic cells of the body. Embryonic stem cells can be maintained as pure stem cellcultures. See: adult stem cellendothelial cell The type of epithelial cell that lines blood vessels and lymph vessels; these cells are usuallysquamous (flattened) and form sheets one layer thick. Endothelial cells are derived frommesenchyme cells of the embryo. A sheet of endothelial cells is called an endothelium.

See: endotheliumenterochromaffin cell Abbreviation: EC cell An enteroendocrine cell that produces serotonin and is found in the small intestine. Enterochromaffin cells are very similar to the cells, found throughout the peripheral sympatheticnervous system, that are called simply 'chromaffin cells'.enteroendocrine cell One of the scattered hormone-producing cells found in the pancreatic islets and throughout thegastrointestinal (mainly, small intestinal) mucosa.ependymal cell Any of the epithelial cells that form a one-cell-thick layer lining the ventricles and the central canal of the central nervous system.

The ventricular (apical) surfaces of many ependymal cells are coveredwith cilia or microvilli. In most places, the ependymal layer does not have a basal lamina.

Specialized regions of ependymal cells include the covering of the blood vessels and looseconnective tissue of the choroid plexuses; here, the ependyma is specialized to secretecerebrospinal fluid.epithelial cell Any of the cells forming the cellular sheets that cover surfaces, both inside and outside the body. Epithelial cells are closely packed and take on polyhedral shapes, from tall (columnar) throughsquat (cuboidal) to flat (squamous). Epithelial cells adhere strongly to one another, and one of theirsurfaces -- the basal surface -- sticks firmly to a thin extracellular film of fibrils called a basal lamina.

A sheet of epithelial cells derived from embryonic epithelia (the ectoderm or the endoderm) is called an epithelium. See: epitheliumethmoidcell Ethmoid sinus.ethmoid air cell Ethmoid sinus.eukaryotic cell The type of cell composing multicellular, as well as a number of unicellular, organisms. Unlikeprokaryotic cells, eukaryotic cells have many of their intracellular functions organized withinstructures called organelles.

Some organelles -- notably, the nucleus, which contains the DNA -- are enclosed by intracellular membranes. F cell An enteroendocrine cell that produces pancreatic polypeptide and is found in the pancreatic islets.fat cell Adipocyte.flame cell A bone marrow cell with a bright red cytoplasm, occasionally found in the marrow of patients withmultiple myeloma.flow cell An optical cell used in photometers and cell counters, through which the sample and any standardsare passed for detection and measured or counted by optical or electrometric means.

See: cytometryfoam cell A cell that contains vacuoles; a lipid-filled macrophage.follicle cell Follicular cell.follicular cell1.

The secretory cell of the thyroid gland; it produces the thyroid hormones, T3 (triiodothyronine) and T4 (tetraiodothyronine or thyroxine).2.

Any of the flattened somatic cells that form a monolayer around each primary oocyte in theovary. After puberty, when an oocyte matures, during a monthly cycle, its follicular cellsdivide, become cuboidal, and form a multilayered coating for the oocyte; at this stage, thefollicular cells are called granulosa cells.folliculostellate cell A supporting cell in the adenohypophysis (anterior pituitary gland); it produces bioactive peptides,including growth factors and cytokines.foreign body giant cell Giant cell. G cell An enteroendocrine cell found in the stomach that produces the hormone gastrin.ganglion cell1. Any neuron whose cell body is located within a ganglion.2. A neuron of the retina of the eye whose cell body lies in the ganglion cell layer.

The axons of ganglion cells form the optic nerve.germ cell A cell whose function is to reproduce the organism. Early in development, primordial germ cells arefound in the genital ridges of the embryo. Later, in the testis, the primordial germ cells are calledspermatogonia, and in the ovary, they are called oogonia. When they mature, the germ cells (i.e.,spermatogonia and oogonia) differentiate into haploid gametes (i.e., spermatozoa and ova).

Synonym: primordial germ cellgiant cell1. A multinucleated phagocyte created by several individual macrophages that have mergedaround a large pathogen or a substance resistant to destruction, such as a splinter or surgical suture.

See: granuloma; tuberculosis2. A large multinucleated (40-60 nuclei) tumor cell characteristic of certain bone and tendontumors.3. A large multinucleated cell that invades the walls of the aorta and its major branches in giant cell arteritis.glial cell One of three types of nonneuronal cell in the central nervous system: astrocytes, oligodendrocytes,and microglial cells. SYN neuroglial cell Synonym: neuroglial cellgitter cell A macrophage present at sites of brain injury.

The cells are packed with lipoid granules fromphagocytosis of damaged brain cells. See: microgliaglobus cell One of the two varieties of basal cell found in the olfactory epithelium. It is a rounded neuroblast or neural stem cell for the olfactory receptor cells.goblet cell A mucous cell sitting between nonsecretory cells, such as is found in the intestinal epithelium.

Golgi cell See: Golgi, Camillogonadotroph cell Gonadotroph.graft facilitating cell Any of a group of CD8 positive, t-cell receptor negative cells that help donated bone marrow engraft in the recipient.granule cell1. Any of the small neurons that pack the granular cell layer of the cerebellar cortex,immediately below the Purkinje cell layer.

Granule cells receive inputs (mossy fibers) from thespinal cord and brainstem (except the inferior olive). Axons of granule cells run perpendicular to the Purkinje cell dendrites, on which they synapse.2. Any of the neurons of the cerebral cortex that are not pyramidal cells.

Cortical granule cellsare categorized as spiny or nonspiny. Synonym: stellate cell3. A small axon-less neuron found in the olfactory bulb.granulosa cell One of the many cuboidal cells that surround and nurture the maturing oocyte. See: follicular cell (2)gustatory cell Taste cell.hair cell An epithelial cell possessing stereocilia in the maculae, cristae ampullaris, and the organ of Corti.

These cells are receptors for the senses of position and hearing.heart failure cell A red-colored (from ingested red cells) lung macrophage often found in the sputum of patients withcongestive heart failure. He La cell A line of human epithelial cells that grows well in culture. It is an immortal cancer cell that has beenmaintained in continuous tissue cultures for decades from a patient with carcinoma of the cervix.

It is named for the first two letters of the patient's first and last names, Henrietta Lacks. He La cellshave been used in thousands of experiments on cell growth, differentiation, and cancer, and in virology, pharmacology, and other fields. HELMET CELLS: (Orig. mag. ×640)helmet cell A schistocyte or fragmented blood cell, seen in hemolytic anemias. See: illustrationhelper cell A type of T lymphocyte whose surface is marked by CD4 receptors; it is involved in both cell-mediated and antibody-mediated immune responses.

It secretes cytokines that stimulate theactivity of B cells and other T cells and binds with class II histocompatibility antigens, which areprocessed by macrophages and other antigen-presenting cells. Synonym: helper T cell See:antigen processing; T cell; cell-mediated immunityhelper T cell Helper cell.hematopoietic stem cell A progenitor cell in the bone marrow that can replicate itself as well as produce precursor cells of the various blood cell lineages.hilus cell An androgen-producing cell found in the ovarian hilum.

It is analogous to the male Leydig cell.holly leaf cell A cell found in blood smears of persons with sickle cell anemia.horizontal cell A neuron of the inner nuclear layer of the retina.

The axons of these cells run horizontally andconnect various parts of the retina. Hürthle cell See: Hürthle cellhybridoma cell See: hybridomahyperchromatic cell A cell that contains more than the normal number of chromosomes and hence stains more densely. I cell An enteroendocrine cell that produces the enzyme cholecystokinin-pancreozymin (pancreaticozymin) and is found in the small intestine.interdigitating cell A type of antigen-presenting cell found in lymph nodes and lymphoid tissue.interstitial cell Any of the many cells found in connective tissue of the ovary, in the seminiferous tubules of thetestes, and in the medulla and cortex of the kidney.

The cells in the testes and ovaries producehormones such as testosterone and estrogen.intestinal absorptive cell In the small intestine, any of the tall columnar cells topped with a brush border made of thousands of microvilli.islet cell A cell of the islets of Langerhans of the pancreas.juvenile cell The early developmental form of a leukocyte.juxtaglomerular cell A modified smooth muscle cell in the wall of the afferent arteriole leading to a glomerulus of thekidney. This type of cell secretes renin when blood pressure decreases to activate the renin-angiotensin mechanism, which increases sodium retention, thus elevating the blood pressure.

K cell An enteroendocrine cell that produces gastric inhibitory peptide (glucose-dependent insulinotropicpeptide) and is found in the small intestine. This peptide stimulates the beta cells of the pancreas to secrete insulin.killer cell Natural killer cell.killer T cell Cytotoxic T cell.

Kulchitsky cell An APUD cell found in the lung. Kupffer cell See: Kupffer cell L cell An enteroendocrine cell that produces glucagon-like peptide-1 and is found in the small intestine.

This peptide signals the pancreas to secrete insulin after a meal.labile cell A cell that is always mitotically active, such as the epithelial cells lining the stomach and the stemcells in the red bone marrow.lactotroph cell Lactotroph. LAK cell Abbreviation for lymphokine-activated killer cell. These natural killer cells, obtained from the patient'sblood, have been activated in culture with interleukin-2.

LAK cells; the cells can then be used to treatpatients with solid malignant tumors. Langerhanscell A type of dendritic antigen-presenting cell that typically resides in the skin. L. E. CELL (center): (Orig. mag. ×1000)L. E. cell Historically, an abbreviation for lupuserythematosus cell, a polymorphonuclearleukocyte that contains the phagocytizednucleus of another cell.

It is characteristic butnot diagnostic of lupus erythematosus. This distinctive cell may form when the blood of patients with systemic lupus erythematosus is incubated and further processed according to a specified protocol. The plasma of some patientscontains an antibody to the nucleoprotein of leukocytes. These altered nuclei, which areswollen, pink, and homogeneous, are ingested by phagocytes.

These are the L. E. cells. Theingested material, when stained properly, is lavender and displaces the nucleus of thephagocyte to the inner surface of the cellmembrane.

The L. E. cell phenomenon can be demonstrated in most patients with systemiclupus erythematosus but is not essential fordiagnosis.illustration Leydig cell See: Leydig's celllittoral cell A macrophage found in the sinuses of lymphatic tissue.liver cell Hepatocyte.lutein cell A cell of the corpus luteum of the ovary that contains fatty yellowish granules.

Granulose lutein cellsare hypertrophied follicle cells; these lutein (paralutein) cells develop from the theca interna.lymphoid cell An obsolete term for lymphocyte.lymphokine-activated killer cell LAK cell. M cell1. A microfold cell, which is a cell in the gastrointestinal epithelium covering patches of lymphoid tissue. M cells transport antigens from the intestinal lumen to the underlyinglymphoid tissues for recognition and processing.2.

An APUD cell that produces melanotropin and is found in the pituitary gland.macroglial cell An astrocyte or an oligodendrocyte.marrow cell Bone marrow cell. MAST CELLmast cell A large tissue cell resembling a basophil, which is essential for inflammatory reactions mediated by immunoglobulin E (Ig E) but does notcirculate in the blood.

Mast cells are presentthroughout the body in connective tissue, butare concentrated beneath the skin and themucous membranes of the respiratory anddigestive tracts. Mast cells are covered with Ig Emolecules, which bind with foreign antigens andstimulate degranulation, releasing suchmediators as histamine, prostaglandins,leukotrienes, and proteinases from denselypacked granules within the cytoplasm. Thesemediators produce type I (immediate)hypersensitivity reactions (e.g., urticaria, allergicrhinitis, asthma, angioedema, and systemicanaphylaxis).

See: illustrationmastoid cell Mastoid air cell.mastoid air cell Any of the variable-sized, air-filled sinuses inside the mastoid antrum. About 20% of adult skullshave no mastoid air cells.matrix stem cell A stem cell derived from Wharton's jelly.memory cell A cell derived from B or T lymphocytes that can quickly recognize a foreign antigen to which thebody has been previously exposed.

Memory T cells stimulate T helper lymphocytes and cytotoxic T cells; memory B cells stimulate the production of antigen-specific antibodies by B plasma cells. Both types of memory cells survive for years, providing a durable adaptive immune response againstforeign antigens.mesenchyme cell One of the two basic somatic cell lineages -- the other being epithelial cells.

In contrast to epithelialcells, mesenchyme cells are not polarized and are frequently motile. In the early embryo,mesenchyme cells fill many of the spaces enclosed by epithelia.

Later, mesenchyme cells willsecrete the space-filling extracellular matrix molecules, such as collagen and glycoproteins, thatcharacterize connective tissue.mesenchymal stem cell A stem cell found in connective tissue and capable of producing cells of the connective tissuelineages, such as cartilage, bone, muscle, and fat cells.mesothelial cell The type of epithelial cell that lines serous (pleural, peritoneal, and pericardial) cavities, bloodvessels, and lymph vessels; these cells are usually squamous (flattened) and form sheets one layerthick.

Mesothelial cells are derived from mesenchyme cells of the embryo. A sheet of mesothelialcells is called a mesothelium.

See: mesotheliummicroglial cell A small glial cell of the central nervous system and retina. Microglia have spiky branched processesand are arranged homogeneously throughout the brain and spinal cord. They are activated by disease and injury, after which they become phagocytic and sometimes resume their embryonicmotility like a macrophage.mitral cell One of the two principal neurons of the olfactory bulb -- the other being the tufted cell.

In a complexsynaptic formation called a glomerulus, each of the mitral and tufted cells receives synaptic inputsfrom axons of the olfactory nerve. The axons of the mitral and tufted cells form the olfactory tractand synapse in the olfactory cortex.mossy cell An astrocyte or other glial cell with many branching processes.

See: neurogliamother cell A cell that gives rise to similar cells through fission or budding. Synonym: parent cellmucosal cell Any cell in a mucosal epithelium.mucous cell An epithelial cell that secretes mucus and Ig A antibodies.

Mucous cells and serous cells are thetwo varieties of secretory cells found in exocrine glands. Synonym: mucus cellmucus cell Mucous cell.multinucleated giant cell Giant cell.multipolar cell Multipolar neuron.muscle cell See: musclemyeloid cell Any white blood cell other than lymphocytes.myeloma cell A cell present in the bone marrow of patients with multiple myeloma.myoepithelial cell A smooth muscle cell found in some epithelia; it lies between glandular cells and the basal lamina of sweat, mammary, lacrimal, and salivary glands. Synonym: basket cellnatural killer cell Abbreviation: NK cell A large granular lymphocyte – a defensive cell of innate immunity – that bonds to cells and lysesthem by releasing cytotoxins.

Natural killer cells are null cells, lymphocytes that do not have B cell or T cell surface markers, and they can be activated without previous antigen exposure. NK cellsdestroy cells infected with viruses and some types of tumor cells in cultures. They also secretegamma interferon (INF? ), tumor necrosis factor alpha (TNFa), and granulocyte-macrophage colony-stimulating factor (GMCSF), enhancing the effect of T lymphocytes.

Synonym: killer cellnerve cell Neuron.neural crest cell Embryonic cells of the neuron-glia lineage that form along the ridges (neural folds) of the neural plateand that migrate into the developing organism to produce a variety of tissues.

The migratory ability of these embryonic epithelial cells is similar to the motility of mesenchyme cells; this has led neuralcrest cells to be called mesectodermal cells. In the neural lineage, neural crest cells give rise to thedorsal root ganglia, the placodes that will develop into the olfactory and auditory sensory organs, thepituitary gland, the peripheral autonomic nervous system, and the neurenteric and APUD cells.

In the glial lineage, neural crest cells give rise to Schwann cells and other peripheral satellite cells. In addition, neural crest cells of the cranial region give rise to certain facial connective tissue, includingthe bones of the nasal cavities, the roof of the mouth, and the sella turcica.neuroglial cell Glial cell.

Niemann-Pick cell See: Niemann-Pick cell NK cell Natural killer cell.nonstem cell Any cell found in the bone marrow that cannot reconstitute the marrow or give rise to moredifferentiated blood cells.null cell A large lymphocyte without the cell markers of either a T cell or a B cell.

Natural killer cells areexamples of null cells.odontoblast cell Odontoblast.oligodendroglial cell Oligodendrocyte.olfactory cell Olfactory receptor cell.olfactory receptor cell A cell of the olfactory mucosa that has receptors for the sense of smell. Olfactory cells arecontinuously replaced from stem cells throughout adult life. Synonym: olfactory cellosteoprogenitor cell Any of the mesenchyme precursor cells committed to the bone lineage and capable of producingosteoblasts and osteocytes.

Osteoprogenitor cells are found in bone, bone marrow, and otherconnective tissue.oxyntic cell A parietal cell of the gastric glands; it produces hydrochloric acid and the intrinsic factor.parabasal cell An abnormal but not malignant cell seen in some cytologic specimens obtained during Papanicolaou tests (Pap tests).

It is found in women with vaginal atrophy, in some postpartumwomen, some women suffering from anorexia or starvation, and some who have used progesteronefor contraception.parent cell Mother cell.phalangeal cell One of the cells supporting the hair cells of the organ of Corti.

These cells form several rows of outerphalangeal cells (Deiters' cells) and a single row of inner phalangeal cells.phantom cell See: red cell ghostpigment cell Any cell that normally contains pigment granules.plasma cell A cell derived from a B lymphocyte that has been sensitized to a specific foreign antigen andproduces antibodies to that particular antigen.

It may be found in the blood or in tissue fluid. Synonym: plasmacytepostganglionic cell Postganglionic neuron. PP cell An enteroendocrine endocrine cell found in the pancreatic islets that produces pancreaticpolypeptide.pre-B cell The immediate precursor of a lymphocytic B cell.preganglionic cell Preganglionic neuron.prickle cell A cell with spiny processes that connect with similar processes of adjoining cells. These are found in the stratum spinosum of the keratinized epithelium of the epidermis.primary cell In physical therapy, a device consisting of a container, two solid conducting elements, and an electrolyte for the production of electric current by chemical energy.primordial cell Primordial germ cell.primordial germ cell A germ cell before it begins its maturation into a haploid gamete.

Synonym: primordial cellprogenitor cell A cell (sometimes a stem cell) that produces cells of a particular lineage, e.g., a neuroblast.prokaryotic cell The form of cell composing many primitive unicellular organisms, such as bacteria. Prokaryotic cells do not have nuclei, which are partitioned by an intracellular membrane; instead the DNA forms onemain coil in the cell cytoplasm.

Purkinje cell See: Purkinje, Johannes E. vonpus cell A leukocyte present in pus. Pus cells are often degenerated or necrotic.pyramidal cell A large, common neuron found in the cerebral cortex.

Pyramidal cells are flask-shaped or triangular,and, in the parts of the cortex with six layers, they occupy the fifth layer. Pyramidal cell dendritesproject up into the most superficial layer of the cortex, while pyramidal cell axons run in theopposite direction, i.e., downward and out of the cortex. Synonym: pyramidal neuronradial glial cell A structural macroglial cell that is a key component of the developing nervous system.

Radial glialcells first appear in the neural tube, where their cell bodies are suspended between two thin cellprocesses; the apical process attaches to the inner (ventricular) surface of the neural tube, and thebasal process attaches to the outer (pial) surface. Early in development, neuroblasts migrateradially along the scaffolding formed by the radial glial cell processes, and growing axons may followthe scaffolding longitudinally.

Later, many radial glial cells retract their processes and differentiateinto astrocytes.red cell A small cell that is filled with hemoglobin, has no nucleus, and is shaped like a biconcave disc. Redcells transport oxygen to tissues and carbon dioxide to the lungs. Individual red cells have a lifespan of 3-4 months, and new red cells are continually being produced in the bone marrow.

In a healthy person, 99% of the cells circulating in the blood are red cells. Synonym: erythrocyte; red blood cell; red blood corpuscle See: erythrocytered blood cell Abbreviation: RBCRed cell.

Renshaw cell See: Renshaw cellresting cell1. A cell that is not dividing. See: interphase2. A cell not performing its normal function (i.e., a nerve cell that is not conducting an impulse or a muscle cell that is not contracting).reticular cell1. An undifferentiated cell of the spleen, bone marrow, or lymphatic tissue that can developinto one of several types of connective tissue cells or into a macrophage.2.

A cell of reticular connective tissue. See: reticular tissuereticuloendothelial cell An out-of-date term for a cell of the mononuclear phagocytic system. Rieder cell See: Rieder cellrod cell A cell in the retina of the eye whose scleral end is long and narrow, forming a rod-shaped sensoryreceptor.

Rods are stimulated by light and are essential for vision in dim light. See: cone cellrosette cell A rose-shaped cluster of phagocytes surrounding lysed nuclear material or red blood cells. Rosettecells occur frequently in blood in which L. E. cells are present. Rosette cells are not diagnostic of lupus erythematosus.

See: L. E. cell Rouget cell See: Rouget cell S cell An enteroendocrine cell that produces secretin and is found in the small intestine.satellite cell1. A stem cell associated with skeletal muscle that may form a limited number of newmuscle cells after injury.2.

One of the neuroglia cells enclosing the cell bodies of sensory neurons in spinal ganglia. Synonym: capsule cellscavenger cell A phagocyte that cleans up disintegrating tissues or cells.

Schwann cell See: Schwann cellsegmented cell A segmented neutrophil (i.e., one with a nucleus of two or more lobes connected by slenderfilaments).selenoid cell See: red cell ghostsensory cell A cell that when stimulated gives rise to nerve impulses that are conveyed to the central nervoussystem.septal cell A type II alveolar cell that secretes pulmonary surfactant; it is adjacent to a septum of the alveoli.serous cell An epithelial cell that secretes a watery fluid containing proteins, glycoproteins, and often antibodies (Ig A, Ig G, and Ig M). Serous cells and mucous cells are the two varieties of secretory cells found in exocrine glands. Sertoli cell See: Sertoli cellsex cell Gamete.

SICKLED CELLS IN SICKLE CELL DISEASEsickle cell An abnormal erythrocyte shaped like a sickle. Synonym: drepanocyte See: anemia, sickle cellillustrationsignet-ring cell A vacuolated cell with the nucleus off center. Mucus-secreting adenocarcinomas usually containthese cells.skeletal muscle cell See: musclesmooth muscle cell See: musclesomatic cell Any cell that is not a germ cell.somatic stem cell Adult stem cell.somatostatin cell D cell.spiculed red cell Crenated red blood cells with surface projections. In most instances, this is a normal variation in redcell equilibrium and is reversible. See: acanthocytespider cell Astrocyte.squamous cell A flat epithelial cell.

Synonym: squamous epithelial cellsquamous epithelial cell Squamous cell.stellate cell1. Granule cell of the cerebral cortex.2. One of the small interneurons found in the outer layer of the cerebellar cortex along withbasket cells.stellate reticuloendothelial cell A Kupffer cell, one of the macrophages that line the sinusoids of the liver.stem cell An embryonic stem cell or an adult stem cell.

Sternberg-Reed cell See: Reed-Sternberg cellstipple cell A red blood cell that contains small basophilic-staining dots. It is seen in lead poisoning, malaria,severe anemia, and leukemia.striated muscle See: musclesuppressor T cell A subpopulation of regulatory T lymphocytes that develop in the thymus gland, that slows or stops a specific immune response.sustentacular cell A supporting cell, as in the acoustic macula, organ of Corti, olfactory epithelium, taste buds, or testes.sympathicotrophic cell One of the large epithelial cells that occur in groups in the hilus of the ovary.

They are thought to be chromaffin cells.sympathochromaffin cell A chromaffin cell of ectodermal origin present in the fetal adrenal gland.

Sympathetic and medullarycells originate from these cells.syncytial giant cell Giant cell. T cell A lymphocyte that responds to specific antigens, with the assistance of antigen-presenting cells (APCs). T cells arise in the bone marrow and migrate to the thymus gland, where they mature; thenthey circulate between blood and lymph, serving as one of the primary cells of the adaptive immuneresponse.

Immature T cells are called thymocytes. Mature T cells are antigen specific. Their surfacereceptors (T cell receptors, abbrev. TCRs) respond only to a single antigen. T cells are furthercategorized using another family of surface protein markers called clusters of differentiation (CDs).

All T cells have a CD3 marker. Additional markers differentiate the subclasses of T cells. CD4 T helper cells serve primarily as regulators, secreting cytokines that stimulate the activities of otherwhite blood cells. CD8 T cells (cytotoxic T cells) directly lyse (kill) organisms, an important defenseagainst viruses; most CD8 T cells also produce gamma interferon (INF?

), one of the strongeststimulators of macrophage activity. Synonym: T lymphocyte See: immune response; lymphocyte; immunological surveillance; T-cell receptor A T cell can only recognize the ""foreignness"" of antigens after they have been modified by macrophages and other antigen-presenting cells (APCs). After this, T cells dominate the adaptiveimmune response by mobilizing B cells and other T cells of the cell-mediated immune pathways.

T cells are responsible for type IV hypersensitivity reactions, such as graft rejection, and for tumor cellrecognition and destruction. See: cytokine; cell-mediated immunity TARGET CELLS: In hemoglobin C disease (×600)target cell1.. An erythrocyte with a dark roundedcentral area surrounded by a lightlystained clear ring, which in turn is surrounded by a dense ring of peripheralcytoplasm.

It is present in certain blooddisorders, such as thalassemia, and in patients who have no spleen. See:hemoglobin C disease for illus Synonym: codocyte; leptocyte2..

The cell at which a signal (e.g., hormone or nerve impulse) is aimed.illustrationtart cell A phagocyte that has ingested the unaltered nuclei of cells. These nuclei can be observedunchanged within the phagocytes.taste cell Any of the neuroepithelial cells within a taste bud that are receptors for the sense of taste. Eachpossesses on the free surface a short gustatory hair that projects through the inner taste pore. Synonym: taste receptor celltaste receptor celltaste cell.tear-drop cell An abnormally shaped blood cell, sometimes found on blood smears of patients with bone marrowfibrosis, iron deficiency, or thalassemias.

Synonym: dacrocytetendon cell Any of the fibroblasts of white fibrous connective tissue of tendons arranged in parallel rows.terminally differentiated cell A cell sufficiently committed to a particular function that it can no longer divide, e.g. a red cell.thymic epithelial cell The epithelial cells that form the internal scaffolding of the thymus. These cells vary in shape andsize but generally align in sheets and cords, partitioning the thymus into islands of close-packedlymphocytes in the organ's cortex.

Thymic epithelial cells are not simply structural and they interactactively with adjacent lymphocytes.thymus cell Any cell characteristic of the thymus, including thymic epithelial cells and thymocytes (thymiclymphocytes).thyroid cell Any cell characteristic of the thyroid gland, but usually referring to a thyroid follicular cell.totipotent cell An undifferentiated embryonic cell that has the potential to develop into any type of cell.

Touton giant cell See: Touton celltransitional cell The stretchable epithelial cells that compose the transitional epithelium (uroepithelium), which linesmost of the urinary tract. Transitional cells are strongly interconnected. They are cuboidal when notunder pressure, and they become flattened and squamous when stretched.

Transitional epithelia are4-6 cells thick, and the top transitional cells -- those on the lumenal surface -- fuse to become largerand polyploid.trophoblast cell One of the epithelial cells forming the surface of the spherical blastocyst stage embryo.

Trophoblastcells are destined to give rise to many of the extraembryonic tissues.tufted See: mitral cell Türk irritation cell See: Türk irritation cell Tzanck cell See: Tzanck cellundifferentiated cell A cell resembling an embryonic cell in that it does not have the specific morphologic or functionalcharacteristics of any particular adult cell type.unipolar cell A cell with a single cell process. Vero cell A lineage of cells used in cell cultures and isolated from kidney epithelial cells of the African greenmonkey ( Cercopithecus aethiops ).visual cell A rod cell or cone cell of the retina.wandering cell A rarely used term for a cell (such as a macrophage) that moves like an ameba.white cell Leukocyte.white blood cell Abbreviation: WBCLeukocyte.

illustration Medical Dictionary, © 2009 Farlex and Partnersprogenitorancestor, including parent.progenitor cellstem cells. Saunders Comprehensive Veterinary Dictionary, 3 ed. © 2007 Elsevier, Inc. All rights reserved›› KEEP READING IN English dictionary Want to thank TFD for its existence?

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wer Gaseous exchange takes place in the lungs' alveoli, which are tiny sacs found at the ends of the terminal bronchioles. The gases that are exchanged are oxygen and carbon dioxide. Continue Reading

Where Does Gaseous Exchange Take Place in the Lungs?

Science Chemistry States of Matter Q: Where Does Gaseous Exchange Take Place in the Lungs? A: Quick Ans

Keep Learning Where Does Gas Exchange Take Place? Where Does Gaseous Exchange Take Place? Where Does Gas Exchange Occur? Credit: Elliott Brown CC-BY-2.0Full Answer The gases can be easily exchanged at the level of the alveoli because these sacs are only one or two cells thick and have a great deal of surface area.

The lungs also contain hundreds of millions of them. The capillaries that flow into the alveoli are also only about one cell thick, and blood cells can only pass through them one at a time. One of the functions of the blood is to get oxygen into the cells of the body. When the blood is depleted of its oxygen, it returns by way of the pulmonary artery to the alveolar capillaries in the lungs.

Once in the alveoli, the carbon dioxide in the blood is expelled by the alveoli up through the bronchi of the lungs and the trachea then expelled from the body through exhalation. At the same time, oxygen enters the alveoli, and the alveoli sends oxygen to the capillaries. The capillaries then give oxygen to the depleted venous blood.

This oxygenated blood is sent through the capillaries toward the heart. Learn more about States of Matter Sources: hyperphysics.phy-astr.gsu.edu mayoclinic.org innerbody.com people.eku.edu Related Questions Q: Alveoli Serve What Function in the Lungs? A: Pulmonary alveoli are the tiny sacs inside the lungs that fill with air with each breath and facilitate the exchange of gas with the blood.

According to Ho... Full Answer >Filed Under: Organs Q: How Does Gaseous Exchange Occur in the Alveoli? A: Gaseous exchange occurs in the alveoli by simple diffusion. The blood flowing past the alveoli is rich in carbon dioxide and very poor in oxygen.

The gas m... Full Answer >Filed Under: Biology Q: What Is the Path That Air Takes When You Take in a Breath? A: When a person takes a breath, the air enters through the nostrils and continues its passage through the pharynx, larynx, trachea, bronchi, bronchioles, lun... Full Answer >Filed Under: Biology Q: What Is the Function of a Respiratory Membrane?

A: The respiratory membrane allows gases to be exchanged between the pulmonary capillaries, or blood vessels, and the respiratory units of the lungs, which co... Full Answer >Filed Under: Organs You May Also Like Q: What Is Plasma Used For?

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it]The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli. Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. Club cells are non-ciliated, rounded protein-secreting cells. Their secretions are a non-sticky, proteinaceous compound to maintain the airway in the smallest bronchioles.

Bronchiole

"This article includes a list of references, but its sources remain unclear because it has insufficient inline citations.

Please help to improve this article by introducing more precise citations. (May 2015) ( Learn how and when to remove this template message)Bronchiole Diagram of the alveoli with both cross-section and external view. Details System Respiratory system Identifiers Latin Bronchioli Me SH D055745TA A06.5.02.026TH H3.05.02.0.00005FMA 7410 76497, 7410Anatomical terminology [ edit on Wikidata]The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa.

They are branches of the bronchi, and are part of the conducting zone of the respiratory system. The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.

Contents [ hide ]1 Structure1.1 Bronchioles1.2 Terminal bronchioles1.3 Respiratory bronchioles2 Clinical significance2.1 Inflammation3 Additional images4 References5 Further reading6 External links Structure [ edit]A lobule of the lung showing r. b respiratory bronchiole; al.

d alveolar duct; a. s alveolar sac; 'a' alveolus A pulmonary lobule is the portion of the lung ventilated by one bronchiole. Bronchioles are approximately 1 mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5 mm or less in diameter. Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where gas exchange takes place.

The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow.

A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow. Bronchioles [ edit]The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi ( tertiary meaning ""third""). The tertiary bronchi subdivide into the bronchioles.

They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have club cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium as the bronchioles decreases in size.

The diameter of the bronchioles is often said to be less than 1 mm, though this value can range from 5 mm to 0.3 mm.

As stated, these bronchioles do not have hyaline cartilage to maintain their patency. Instead, they rely on elastic fibers attached to the surrounding lung tissue for support. The inner lining ( lamina propria) of these bronchioles is thin with no glands present, and is surrounded by a layer of smooth muscle.

As the bronchioles get smaller they divide into terminal bronchioles. These bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, from the sixteenth through the twenty-third division of the tract. Terminal bronchioles [ ed

Bronchiole

us A pulmonary lobule is the portion of the lung ventilated by one bronchiole. Bronchioles are approximately 1 mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5 mm or less in diameter.

Bronchiole

Please help to improve this article by introducing more precise citations. (May 2015) ( Learn how and when to remove this template message)Bronchiole Diagram of the alveoli with both cross-section and external view. Details System Respiratory system Identifiers Latin Bronchioli Me SH D055745TA A06.5.02.026TH H3.05.02.0.00005FMA 7410 76497, 7410Anatomical terminology [ edit on Wikidata]

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system.

The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.

Contents [ hide ]1 Structure1.1 Bronchioles1.2 Terminal bronchioles1.3 Respiratory bronchioles2 Clinical significance2.1 Inflammation3 Additional images4 References5 Further reading6 External links Structure [ edit]A lobule of the lung showing r. b respiratory bronchiole; al. d alveolar duct; a. s alveolar sac; 'a' alveol

Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where gas exchange takes place.

The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow. A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow.

Bronchioles [ edit]The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi ( tertiary meaning ""third""). The tertiary bronchi subdivide into the bronchioles.

They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have club cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium as the bronchioles decreases in size. The diameter of the bronchioles is often said to be less than 1 mm, though this value can range from 5 mm to 0.3 mm.

As the bronchioles get smaller they divide into terminal bronchioles. These bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, from the sixteenth through the twenty-third division of the tract.

Terminal bronchioles [ edit]The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli.

Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. Club cells are non-ciliated, rounded protein-secreting cells. Their secretions are a non-sticky, proteinaceous compound to maintain the airway in the smallest bronchioles.

dit]Bronchospasm, a potentially life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. The most common cause of this is asthma. Bronchospasm is commonly treated by oxygen therapy and bronchodilators

ase increased airway resistance decreases airway ventilation [Bronchioles are made of smooth muscle, not cartilage, so it can contract or relax, and in asthmatics they contract (due to allergens or exercise) restricting airflow]; alveolar PO2: low arterial PO2: loww

Respiratory System Part Dos

20 terms sniemeyer Respiratory System Part Dos Learn Flashcards Write Spell Test Match Gravity Advertisement Upgrade to remove ads Like this study set?

Create a free account to save it. Create a free account Maybe later Sortwhat is the normal PO2 in the alveoli 100what is normal arterial PO2 after gas exchange occurs 100what is the PO2 of venous blood 40what occurs in emphesyma; what happens to blood and alveolar PO2 in this case destruction of alveoli reduces surface area for gas exchange; blood PO2: low alveolar PO2: normal or low (low due to ventilation airway blockage)what occurs in fibrotic lung disease; what happens to blood and alveolar PO2 in this case thickened alveolar membrane slows gas exchange, loss of lung compliance may decrease alveolar ventilation; alveolar PO2: normal to low (low if you exercise or if fibrotic condition is extreme) arterial PO2: lowwhat occurs in pulmonary edema; what happens to blood and alveolar PO2 in this case fluid in interstitial space increases diffusion distance, arterial PO2 may be normal due to higher CO2 solubility in water; alveolar PO2: normal arterial PO2: lowwhat occurs during asthma; what happens to blood and alveolar PO2 in this c

hat do asthmatics take to relax their bronchioles epinephrinehow does venous blood flow and gas exchange correlate Venous blood flow has to match up with gas exchange so they can occur at the same ratewhat is the local control mechanism to try to keep ventilation and perfusion matched decreased tissue PO2 around under-ventilated alveoli constricts their arterioles, diverting blood to better ventilated alveoliwhy is the local control mechanism to try and keep ventilation and perfusion matched not good at altitude because there is less PO2 overall in the lungs, leading to constriction of all arterioles, leading to less O2 carrying ability throughout the lungswhat happens to bronchioles, pulmonary arterioles, and systemic arterioles when PCO2 increases bronchioles: dialate pulmonary arterioles: (constrict) systemic arterioles: dialatewhat happens to bronchioles, pulmonary arterioles, and systemic arterioles when PCO2 decreases bronchioles: constrict pulmonary arterioles: (dialate) systemic arterioles: constrictwhat happens to bronchioles, pulmonary arterioles, and systemic arterioles when PO2 increases bronchioles: (constrict) pulmonary arterioles: dialate systemic arterioles: constrictwhat happens to bronchioles, pulmonary arterioles, and systemic arterioles when PO2 decreases bronchioles: (dialate) pulmonary arterioles: constrict systemic arterioles: dialatewhere are peripheral chemoreceptors located in glomus cells in the carotid arterieswill the peripheral chemoreceptors sense low PO2 during exercise no, low PO2 in peripheral chemoreceptors does NOT happen during exercise; afferent neurons in muscle itself test this; they will fix it before you get to the carotid arterieswhen will peripheral chemoreceptors sense low PO2 at altitude or if you have some sort of pathological disease; peripheral chemoreceptors don't discharge until arterial PO2 gets down to 60-70mm Hg PO2look at a youtube video on how peripheral chemoreceptors cause exocytosis in glomus cells; also look at one for central ...what do central chemoreceptors respond to arterial PCO2 (not the venous side!

), changes in p H, and arterial PO2 (Really senses p H changes not CO2 as much (because CO2 actually leads to change in p H as it makes HCO3-)Advertisement Upgrade to remove ads Features Quizlet Live Quizlet Learn Diagrams Flashcards Mobile Help Sign up Help Center Honor Code Community Guidelines Students Teachers About Company Press Jobs Privacy Terms Follow us Language© 2018 Quizlet Inc.

This essential fluid is produced by the Type II alveolar cells, and lines the alveoli and smallest bronchioles. Surfactant reduces surface tension throughout the lung, thereby contributing to its general compliance.

Surfactant

Surfactant Surfactant is a complex substance containing phospholipids and a number of apoproteins.

It is also important because it stabilizes the alveoli. LaplaceÕs Law tells us that the pressure within a spherical structure with surface tension, such as the alveolus, is inversely proportional to the radius of the sphere (P=4T/r for a sphere with two liquid-gas interfaces, like a soap bubble, and P=2T/r for a sphere with one liquid-gas interface, like an alveolus: P=pressure, T=surface tension, and r=radius).

That is, at a constant surface tension, small alveoli will generate bigger pressures within them than will large alveoli. Smaller alveoli would therefore be expected to empty into larger alveoli as lung volume decreases.

This does not occur, however, because surfactant differentiallyreduces surface tension, more at lower volumes and less at higher volumes, leading to alveolar stability and reducing the likelihood of alveolar collapse. Surfactant is formed relatively late in fetal life; thus premature infants born without adequate amounts experience respiratory distress and may die.

See Also: Alveoli Send comments about this page to the Office of Academic Computing (OAC) at oac@jhmi.edu. Copyright © 1995 Johns Hopkins University

Bronchiole

"This article includes a list of references, but its sources remain unclear because it has insufficient inline citations.

Please help to improve this article by introducing more precise citations. (May 2015) ( Learn how and when to remove this template message)Bronchiole Diagram of the alveoli with both cross-section and external view. Details System Respiratory system Identifiers Latin Bronchioli Me SH D055745TA A06.5.02.026TH H3.05.02.0.00005FMA 7410 76497, 7410Anatomical terminology [ edit on Wikidata]

The bronchioles or bronchioli are the passageways by which air passes through the nose or mouth to the alveoli (air sacs) of the lungs, in which branches no longer contain cartilage or glands in their submucosa. They are branches of the bronchi, and are part of the conducting zone of the respiratory system.

The bronchioles divide further into smaller terminal bronchioles which are still in the conducting zone and these then divide into the smaller respiratory bronchioles which mark the beginning of the respiratory region.

Contents [ hide ]1 Structure1.1 Bronchioles1.2 Terminal bronchioles1.3 Respiratory bronchioles2 Clinical significance2.1 Inflammation3 Additional images4 References5 Further reading6 External links Structure [ edit]A lobule of the lung showing r. b respiratory bronchiole; al. d alveolar duct; a. s alveolar sac; 'a' alveol

us A pulmonary lobule is the portion of the lung ventilated by one bronchiole. Bronchioles are approximately 1 mm or less in diameter and their walls consist of ciliated cuboidal epithelium and a layer of smooth muscle. Bronchioles divide into even smaller bronchioles, called terminal, which are 0.5 mm or less in diameter.

Terminal bronchioles in turn divide into smaller respiratory bronchioles which divide into alveolar ducts. Terminal bronchioles mark the end of the conducting division of air flow in the respiratory system while respiratory bronchioles are the beginning of the respiratory division where gas exchange takes place.

The diameter of the bronchioles plays an important role in air flow. The bronchioles change diameter to either increase or reduce air flow. An increase in diameter is called bronchodilation and is stimulated by either epinephrine or sympathetic nerves to increase air flow. A decrease in diameter is called bronchoconstriction and is stimulated by histamine, parasympathetic nerves, cold air, chemical irritants and other factors to decrease air flow.

Bronchioles [ edit]The primary bronchi, in each lung, which are the left and right bronchus, give rise to secondary bronchi. These in turn give rise to tertiary bronchi ( tertiary meaning ""third""). The tertiary bronchi subdivide into the bronchioles.

They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have club cells in their epithelial lining. The epithelium starts as a simple ciliated columnar epithelium and changes to simple ciliated cuboidal epithelium as the bronchioles decreases in size. The diameter of the bronchioles is often said to be less than 1 mm, though this value can range from 5 mm to 0.3 mm.

As stated, these bronchioles do not have hyaline cartilage to maintain their patency. Instead, they rely on elastic fibers attached to the surrounding lung tissue for support. The inner lining ( lamina propria) of these bronchioles is thin with no glands present, and is surrounded by a layer of smooth muscle.

As the bronchioles get smaller they divide into terminal bronchioles. These bronchioles mark the end of the conducting zone, which covers the first division through the sixteenth division of the respiratory tract. Alveoli only become present when the conducting zone changes to the respiratory zone, from the sixteenth through the twenty-third division of the tract.

Terminal bronchioles [ edit]The terminal bronchiole is the most distal segment of the conducting zone. It branches off the lesser bronchioles. Each of the terminal bronchioles divides to form respiratory bronchioles which contain a small number of alveoli.

Terminal bronchioles are lined with simple cuboidal epithelium containing club cells. Terminal bronchioles contain a limited number of ciliated cells and no goblet cells. Club cells are non-ciliated, rounded protein-secreting cells. Their secretions are a non-sticky, proteinaceous compound to maintain the airway in the smallest bronchioles.

dit]Bronchospasm, a potentially life-threatening situation, occurs when the smooth muscular tissue of the bronchioles constricts, severely narrowing their diameter. The most common cause of this is asthma. Bronchospasm is commonly treated by oxygen therapy and bronchodilators

What are Bronchioles The smallest airways within the lungs that are not encircled by any cartilage are called bronchioles [1]. Once the trachea divides into the left and right primary bronchi, they then branch into smaller and smaller divisions to lead to bronchioles.

What are Bronchioles

The trachea, bronchi, bronchioles, and alveoli all make up the lower respiratory tract [2]. Each lung has around 30,000 bronchioles [3]. Bronchioles Diagram Location and Structure Located within the lungs, bronchioles are tubular structures around 1mm in diameter [4], consisting of connective tissues and some smooth muscles that keep the tubes open.

These further divide into smaller tubules, which in turn continue subdividing till they reach the alveoli. Most parts of the bronchioles are lined with ciliated pseudostratified columnar or cuboidal epithelial tissues containing goblet cells. Bronchiole Histology Lobular Bronchioles Also called preterminal bronchioles, each lobular bronchiole branches into multiple terminal bronchioles after passing into a pulmonary lobule [5].

Terminal Bronchioles Smaller tubules of around 0.5mm diameter, with ciliated cuboidal epithelium (there are no goblet cells) [6]. As their name suggests, these are considered the last conducting structure of the human respiratory system, eventually terminating in respiratory bronchioles [6, 7]Terminal Bronchiole Histology Respiratory Bronchioles The final division of bronchioles, these end in 2-11 alveolar ducts [7, 8], surrounded by the proteins elastin and collagen, and smooth muscles, each leading into an alveolar sac.

These sacs contain multiple alveoli, encircled by pulmonary system blood vessels [9]. Ciliated cuboidal epithelial cells line the respiratory bronchioles, while some non-ciliated cells, known as clara cells, are present as well [6].

Any dust particles and germs present in the inhaled air stick to the mucus secreted by the goblet cells in the epithelium, so the cilia can ‘sweep’ it upward to be excreted through the oral or nasal cavity [10]. What are the Functions of the Bronchioles As the oxygen-rich inhaled air reaches the lungs through the bronchi, it travels via bronchioles to reach the alveoli, where the gas exchange (oxygen moving into blood, and carbon dioxide moving into the alveoli to be carried out during exhalation) occurs [7].

The bronchioles play a most important role in the respiratory system by making sure each and every alveolus is supplied with oxygen [11]. Associated Conditions Bronchiolitis: A common infectious condition that causes swelling and inflammation of the bronchioles, and may affect the lungs in some cases.

It often leads to coughing, congestion, and difficulty breathing due to an accumulation of mucus that blocks the airways.

Bronchiolitis usually affects infants and toddlers below 2-3 years of age [12]. Bronchiectasis: Characterized by permanent damage and dilation of the bronchi and bronchioles, it may occur as a result of certain genetic disorders, abnormal immune system functioning, and allergies of the lungs.

Symptoms include a chronic cough, chest pain, wheezing, shortness of breath, and fatigue. It is incurable, but proper management enables an affected individual to lead a normal life [13]. Bronchospasm: A sudden constriction of the walls of bronchi and bronchioles, often occurring due to chronic asthma and allergies, it may cause wheezing, shortness of breath, coughing, and chest tightness.

Treatment involves managing the underlying condition and avoiding triggering factors [14, 15]. Emphysema: A type of chronic obstructive pulmonary disease (COPD), it is characterized by inflammation of the airways within the lungs that makes the bronchioles lose their elasticity and collapse during breathing. The inhaled air then gets trapped within the alveoli, resulting in difficulty breathing [16]. Smoking is considered the primary cause of the condition with treatment involving medications to open up the passages and avoiding triggers [17]. References +

nx. At the end of the smallest bronchioles are tiny air sacs called alveoli. Alveoli are lined by a very thin layer of cells. They also have an excellent blood supply. The tiny alveoli are the place where oxygen enters the blood and where carbon dioxide (CO 2) leaves the blood.

Where are the lungs found?

Where are the lungs found? The lungs are found in the chest on the right and left side. At the front they extend from just above the collarbone (clavicle) at the top of the chest to about the sixth rib down. At the back of the chest the lungs finish around the tenth rib. The protective linings which cover the lungs (pleura) continue down to the twelfth rib.

From front to back the lungs fill the rib cage but are separated by the heart, which lies in between them. The lungs are divided into different parts which are called lobes. The right lung has three lobes called upper, middle and lower lobes.

The left lung only has two lobes, the upper and lower. The air that we breathe in enters the nose or mouth, flows through the throat (pharynx) and voice box (larynx) and enters the windpipe (trachea). The trachea divides into two hollow tubes called bronchi. The right main bronchus (bronchus is the word for one of the bronchi) supplies the right lung; the left main bronchus supplies the left lung.

These bronchi then go on to divide into smaller bronchi. The small bronchi divide into smaller and smaller hollow tubes which are called bronchioles - the smallest air tubes in the lungs. The medical term for all the air tubes from the nose and mouth down to the bronchioles is 'the respiratory tract'. The lower respiratory tract is from the lary

What do the lungs do? The lungs' main function is to help oxygen from the air we breathe enter the red cells in the blood. Red blood cells then carry oxygen around the body to be used in the cells found in our body. The lungs also help the body to get rid of CO 2 gas when we breathe out.

There are a number of other jobs carried out by the lungs that include: Changing the p H of blood (whether the blood is more acid or alkali) by increasing or decreasing the amount of CO 2 in the body.

Filtering out small gas bubbles that may occur in the bloodstream. Converting a chemical in the blood called angiotensin I to angiotensin II. These chemicals are important in the control of blood pressure. How do the lungs and breathing work? Breathing in is called inhalation. The most important muscle of inhalation is the diaphragm. Found beneath the lungs, the diaphragm is a dome-shaped muscle.

When this muscle gets tighter (contracts), it flattens and the lungs increase in size. This sucks air down into your lungs. Some of the oxygen in the air can then be transferred into your bloodstream. Some of the carbon dioxide in your blood is transferred into the air that is in your lungs.

This controls the levels of oxygen and carbon dioxide in your bloodstream. See also the separate leaflet called The Heart and Blood Vessels for more information on how blood is pumped to the lungs and to the rest of your body. Breathing out (exhalation) is the opposite of inhalation. The diaphragm and other chest muscles relax.

This makes the lungs decrease in size so that air is pushed back out of your lungs and out through your mouth or nose. The basic rhythm of breathing is controlled by the brain. Part of the brain called the brainstem has a special area dedicated to maintaining your breathing pattern. Nerve impulses from the brainstem control the contractions of your diaphragm and the other muscles of breathing. This is all done without thinking. However, other parts of the brain can temporarily overrule the brainstem.

This is how we are able consciously to hold our breath or change our pattern of breathing. While the brain controls the basic rhythm of breathing, it also receives information from sensors in the body. These sensors are nerve cells and provide information that influences the rate and depth of breathing.

The main sensors monitor levels of CO 2 in the blood. When the level of CO 2 rises, the sensors send electrical impulses to the brain. These impulses cause the brain to send more electrical signals to the muscles of breathing. Breathing then gets deeper and faster and more CO 2 is breathed out (exhaled).

The blood level of CO 2 then decreases back to the normal level. Some disorders of the respiratory tract, lung and chest Asthma Bornholm disease Bronchiectasis Cancer of the lung Chronic obstructive pulmonary disease Cystic fibrosis Hiccups (hiccoughs)Idiopathic pulmonary fibrosis Pleural effusion Pleurisy Pneumothorax Pulmonary embolism Sarcoidosis Sleep apnoea Some infections of the respiratory tract Bronchiolitis Bronchitis Colds Cough Epiglottitis Laryngitis Legionnaires' disease Pneumonia Sinusitis Sore throat Tonsillitis Tuberculosis Upper respiratory tract infections Whooping cough The diagram below shows in which part of the respiratory tract some of the infections are located: Respiratory tract infections Read about sinusitis , tonsillitis, pharyngitis , laryngitis, tracheitis, pleurisy, bronchitis and pneumonia. Further more detailed information available free online The Respiratory Apparatus From Gray's Anatomy Online Web: www.bartleby.com/107/235.html Human Physiology/The Respiratory System From Wikibooks, the open-content textbooks collection Web: http://en.wikibooks.org/wiki/Human_Physiology/The_respiratory_system

A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate.

Gas Exchange

Gas Exchange Learning Objectives By the end of this section, you will be able to: Compare the composition of atmospheric air and alveolar air Describe the mechanisms that drive gas exchange Discuss the importance of sufficient ventilation and perfusion, and how the body adapts when they are insufficient Discuss the process of external respiration Describe the process of internal respiration The purpose of the respiratory system is to perform gas exchange.

Pulmonary ventilation provides air to the alveoli for this gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting.

It is through this mechanism that blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body. Gas Exchange In order to understand the mechanisms of gas exchange in the lung, it is important to understand the underlying principles of gases and their behavior.

In addition to Boyle’s law, several other gas laws help to describe the behavior of gases. Gas Laws and Air Composition Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure.

In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 1). Table 1. Partial Pressures of Atmospheric Gases Gas Percent of total composition Partial pressure (mm Hg)Nitrogen (N 2) 78.6 597.4Oxygen (O 2) 20.9 158.8Water (H 2 O) 0.04 3.0Carbon dioxide (CO 2) 0.004 0.3Others 0.0006 0.5Total composition/total atmospheric pressure 100% 760.0Partial pressure ( P x) is the pressure of a single type of gas in a mixture of gases.

For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 1).

Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture. Figure 1. Partial pressure is the force exerted by a gas. The sum of the partial pressures of all the gases in a mixture equals the total pressure.

Partial pressure is extremely important in predicting the movement of gases. Recall that gases tend to equalize their pressure in two regions that are connected. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower.

In addition, the greater the partial pressure difference between the two areas, the more rapid is the movement of gases. Solubility of Gases in Liquids Henry’s law describes the behavior of gases when they come into contact with a liquid, such as blood. Henry’s law states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas. The greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid.

For example, although nitrogen is present in the atmosphere, very little nitrogen dissolves into the blood, because the solubility of nitrogen in blood is very low. The exception to this occurs in scuba divers; the composition of the compressed air that divers breathe causes nitrogen to have a higher partial pressure than normal, causing it to dissolve in the blood in greater amounts than normal.

Too much nitrogen in the bloodstream results in a serious condition that can be fatal if not corrected. Gas molecules establish an equilibrium between those molecules dissolved in liquid and those in air.

The composition of air in the atmosphere and in the alveoli differs. In both cases, the relative concentration of gases is nitrogen > oxygen > water vapor > carbon dioxide. The amount of water vapor present in alveolar air is greater than that in atmospheric air (Table 2). Recall that the respiratory system works to humidify incoming air, thereby causing the air present in the alveoli to have a greater amount of water vapor than atmospheric air. In addition, alveolar air contains a greater amount of carbon dioxide and less oxygen than atmospheric air.

This is no surprise, as gas exchange removes oxygen from and adds carbon dioxide to alveolar air. Both deep and forced breathing cause the alveolar air composition to be changed more rapidly than during quiet breathing. As a result, the partial pressures of oxygen and carbon dioxide change, affecting the diffusion process that moves these materials across the membrane.

This will cause oxygen to enter and carbon dioxide to leave the blood more quickly. Table 2. Composition and Partial Pressures of Alveolar Air Gas Percent of total composition Partial pressure (mm Hg)Nitrogen (N 2) 74.9 569Oxygen (O 2) 13.7 104Water (H 2 O) 6.2 40Carbon dioxide (CO 2) 5.2 47Total composition/total alveolar pressure 100% 760.0Ventilation and Perfusion Two important aspects of gas exchange in the lung are ventilation and perfusion.

Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible.

However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced. The partial pressure of oxygen in alveolar air is about 104 mm Hg, whereas the partial pressure of the oxygenated pulmonary venous blood is about 100 mm Hg. When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high.

In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops. Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem. In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation.

This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation. At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and p H levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli. Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli.

A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate.

As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow. Gas Exchange Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up.

External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes.

Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs.

External Respiration The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries.

These pulmonary capillaries create the respiratory membrane with the alveoli. As the blood is pumped through this capillary network, gas exchange occurs.

Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes (red blood cells) and binds to a protein called hemoglobin, a process described later in this chapter. Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli. Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter.

External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries. Figure 2. In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus.

Although the solubility of oxygen in blood is not high, there is a drastic difference in the partial pressure of oxygen in the alveoli versus in the blood of the pulmonary capillaries. This difference is about 64 mm Hg: The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg.

This large difference in partial pressure creates a very strong pressure gradient that causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood. The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary.

However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids.

As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar. Internal Respiration Internal respiration is gas exchange that occurs at the level of body tissues (Figure 3).

Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low, about 40 mm Hg, because oxygen is continuously used for cellular respiration.

In contrast, the partial pressure of oxygen in the blood is about 100 mm Hg. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue.

Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy in color. Figure 3. Oxygen diffuses out of the capillary and into cells, whereas carbon dioxide diffuses out of cells and into the capillary. Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood.

It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg.

The blood is then pumped back to the lungs to be oxygenated once again during external respiration. Everyday Connections: Hyperbaric Chamber Treatment A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment.

A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber.

Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia.

Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized.

Figure 4. Hyperbaric Chamber (credit: “komunews”/flickr.com)Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure.

In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning.

Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream.

At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen.

An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair.

Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures. Chapter Review The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture.

Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure.

The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli.

The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar. Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli.

If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation.

External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences. Self Check Answer the question (s) below to see how well you understand the topics covered in the previous section.22.4 Exercise 27.

Check Your Understanding Critical Thinking Questions Compare and contrast Dalton’s law and Henry’s law. A smoker develops damage to several alveoli that then can no longer function. How does this affect gas exchange?

Show Answers Glossary Dalton’s law: statement of the principle that a specific gas type in a mixture exerts its own pressure, as if that specific gas type was not part of a mixture of gasesexternal respiration: gas exchange that occurs in the alveoli Henry’s law: statement of the principle that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gasinternal respiration: gas exchange that occurs at the level of body tissuespartial pressure: force exerted by each gas in a mixture of gasestotal pressure: sum of all the partial pressures of a gaseous mixtureventilation: movement of air into and out of the lungs; consists of inspiration and expiration Licenses and Attributions Previous Next

In addition to defense, the Clara cells help the terminal bronchiole to remain open as air passes through it. They release a type of substance known as a surfactant, which decreases the tension of the epithelial lining of the bronchiole. this makes expansion of the airway possible as air is inhaled.

What Is a Terminal Bronchiole?

A terminal bronchiole is a tiny airway transporting air in and out of the lungs. The second to last branch of the bronchi, a terminal bronchiole is a subdivision of the bronchioles and itself branches into the respiratory bronchioles. These bronchioles directly penetrate the alveoli, the bud-like sacs filled with capillaries where oxygen and carbon dioxide enter and leave the bloodstream.

This respiratory airway is known as a terminal bronchiole because it is the final pathway of the conducting zone.

The conducting zone includes all segments of the respiratory system up until this point — among them the nose, trachea, bronchi, and bronchioles — and functions to increase the temperature of and add moisture to the incoming air, as well as filter it of pathogens. Ad Beginning where it enters the nose via the nostrils, inhaled air is swept into the nasal cavity and backward into the pharynx or throat.

Passing through the larynx, better known as the voice box, it is drawn into the trachea by the action of the diaphragm muscle beneath the lungs, which fills the underside of the rib cage and acts like a suction cup when it contracts.

Air pulled into the trachea splits off into either lung by way of the bronchi, which feature many tiny branches, the bronchioles.

If the lungs were a budding tree, then the trachea or windpipe would be the trunk, the two bronchi would each be a branch, the bronchioles the limbs splitting off these branches, the terminal bronchioles the twigs on the limbs, the respiratory bronchioles the stems of the leaves on the twigs, and the alveoli the buds of the leaves.

As the final portion of the conducting zone, the terminal bronchiole performs the same functions as the segments before it. It warms the air, contributes moisture, filters and encourages continued airflow by expanding to decrease any resistance met by the incoming air as it makes its way toward the alveoli.

The last two functions are of particular importance, as the air that reaches each terminal bronchiole is already nearly warmed to body temperature and moistened. At this point, the air also been fairly well stripped of pathogens. In fact, terminal bronchioles contain few ciliated cells, the cells found throughout the conducting zone whose job is to collect allergens and other unwanted particles carried in inhaled air.

Instead, they are lined with a type of unciliated epithelial cell known as a Clara cell, which secretes a protein known as Clara cell secretory protein (CCSP) whose enzymes break up toxins found in the air as well as suspended in lung fluid.

Conversely, as air is expired from the lungs, the surfactant prevents the vacuum created by exhalation from sucking the tube-shaped bronchiole shut.

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This bronchiole gets subdivided into respiratory bronchioles which comprise of only a few alveoli. Simple cuboidal epithelium, comprising of Clara cells, line the Terminal bronchioles.

Terminal bronchiole

Terminal bronchiole By Shoummojit Roy on July 14, 2012 in Respiratory System4.2 (84.44%) 9 votes Terminal bronchiole Definition It is the terminal section of the nonrespiratory conducting airway. This bronchiole gets subdivided into respiratory bronchioles. The Terminal bronchioles are referred to as the last of the purely conductive airway generations in the human lungs.

Terminal bronchiole Location It is located at the terminus of the conducting zone. It has a diameter that approximately ranges between 0.5 to 1 mm. Terminal bronchiole Anatomy

The walls of the Terminal bronchioles contain only a small number of ciliated cuboidal cells, connective tissues and a limited number of smooth muscle cells. Terminal bronchiole Function It supplies oxygen to each pulmonary acini in the body. The main function of these tubular structures is conduction of gas and they are too thick to allow the exchange of air.

Terminal bronchiole Pictures Check out these useful images to know how these bronchioles look like. Picture 1 – Terminal bronchiole Picture 2 – Terminal bronchiole Image References:http://en.wikipedia.org/wiki/Terminal_bronchiolehttp://medical-dictionary.thefreedictionary.com/terminal+bronchiolehttp://medcell.med.yale.edu/histology/respiratory/terminal_bronchiole_cross_section.phphttp://www.britannica.com/EBchecked/topic/587966/terminal-bronchiole Last updated on February 1st, 2018 at 12:52 pm About Shoummojit Roy View all posts by Shoummojit Roy →

The ciliated epithelium in the lung is located on the inside of the bronchioles. The cilia and the moist surface lining captures dirt or toxins that are inhaled.

Where is epithelial tissue in the lungs?

Answers.com ® Wiki Answers ® Categories Science Biology Human Anatomy and Physiology Respiratory System Lungs Where is epithelial tissue in the lungs?

Flag Where is epithelial tissue in the lungs? Answered by The Wiki Answers ®Community Answers.com ® is making the world better one answer at a time. You can find simple squamous epithelial tissue in alveoli in lungs. The reason of it, is that simple squamous cells are very thin and they pass the gases through very easily.

As you know the alveoli's' role is to exchange oxygen and carbon dioxide, thin walls help to do it quicker.4 people found this useful Was this answer useful? Yes Somewhat No What does epithelial tissue do? It protects the organism from microorganisms, injury, fluid loss, and it's organs.12345TD 3,231 Contributions What Type of epithelial in lungs? The ciliated columnar epithelium lines the trachea (windpipe) and bronchi (lungs). The squamous epithelium forms the delicate lining of cavities (nose and alveoli etc. )What is the role of ciliated epithelial in the lung?

This is cough …Dina S. 5 Contributions What epithelial tissue is found in the lung tissue? The lung tissue (the lower respiratory tract) is composed of non ciliated columnar epithelium while the tissue of the upper respiratory tract is of the ciliated type.

Ahmadbtm 3,398 Contributions What epithelial tissues form walls of capillaries and air sacs of lungs? Simple squamus Alea Iacta Est 3,228 Contributions Binds epithelial tissue to underlining tissues? Basal membrane. Is epithelial tissue a connective tissue?no, there are 4 different classes of tissue epithelial,connective, muscular, and nervous.

What do epithelial cells in the lungs do?they have tiny hairs and clean out dirt, also they are permeable and absorb substances quickly in gas exchange What respiratory tubes found in the lungs are lined with epithelial tissue and held open by varying amounts of cartilage?bronchioles Tim Mullican 2,269 Contributions How can you tell epithelial tissue from other tissue? Epithelial tissue has a free surface, a basement membrane, and little intercellular material. What kind of epithelial tissue is found in alveolar sacs of the lungs?

Simple Squamous What is the medical term meaning glandular tumor of epithelial tissue of the lung?adenocarcincoma Joseph Kay 56 Contributions Answered In Biology Can a epithelial tissue be called as semipermeable tissue?

Yes Answered In Lungs Why are the alveoli in the lungs lined with simple squamous epithelial tissue?where rapid gas exchange occurs, as oxygen enters the bloodstream through alveolar blood vessels and carbon dioxide exits as waste. Penthesiliea 1,944 Contributions Answered In Human Anatomy and Physiology Is epithelial a tissue? Yes.

Answered In Capillaries What are the tiny air sacs within the lungs that are made of a single layer of squamous epithelial tissue and are covered with very small capillaries?alveoli Ligand 7,255 Contributions Answered In Medical Definitions and Word Differences What is epithelial tissue? Epithelial tissue forms lining layers of structures in the body. Examples There is epithelial tissue in the skin. Epithelial tissue forms the inner lining of the st …

(red) The acinus is magnified in the next image (6), showing first the tubular terminal bronchiole branching into the respiratory bronchioles, alveolar sacs, and finally the grape like alveoli. The organization of the connective tissues of the lung is shown in image 7.

"The Lung Introduction The lungs are two huffing and puffing sponge-like organs that dominate the chest cavity, essential in their function as the principle structures of respiration. An understanding of their unique anatomy and physiology brings understanding of how diseases will affect the lungs, and how these changes will be manifest on x-ray and CT evaluation.

In this first part of the series on the lung we emphasize principles, and outline how structure is integrated with function, disease and imaging.

The unique structural characteristics of the lungs include their:dominance in the chest cavityability to accommodate the entire cardiac output with every heartbeatasymmetric natureirregular and dichotomous branch pattern of the bronchovascular bundletubular transport system, with a single system functioning for both delivery and removalspongy air-filled characterpyramidal or cone shapedual blood supply The unique functional aspects include The ability to move air efficiently The ability to exchange gases efficiently Lung Structure This collage reflects the anatomic range of the respiratory system from the macroscopic to the microscopic - a continuum of structure.

Image 2 is a post-mortem specimen taken from the front and slightly above. It shows the trachea and bronchi supplying the two lungs above, with the aortic arch and cardiac structures in the middle and below. Note how pink the lungs are in this specimen from an unfortunate baby with congenital heart disease. Image 3, the chest x-ray, shows the lucent lungs within the thoracic cavity while image 4 is a diagram of the trilobed right lung and the bilobed left lung.

Two respiratory units of the lung are shown in the next image each called a pulmonary lobule (5). The lobule consists of a central bronchiole (light blue) and pulmonary arteriole (dark blue), surrounded by the air filled acinus (teal) with its peripheral venules.

Finally we get down to the grapes or alveoli of the lung with surrounding vessels (8), and a single alveolus is seen in 9. It seems a long way for the air to travel but the system can deliver the air to and from the outside in a single breath, and exchange the gases at the capillary level even more rapidly.

It is a remarkable system. Courtesy Ashley Davidoff MD 42651c Overview As we progress through the module there is a recurring pattern of the dual function of the respiratory apparatus – an airway system that transports the air, and an exchange system that enables transfer of the gases across the alveolar membrane.

Lung Structure There are two major functional components to the lungs; the transport system and the exchange system. The first image is a reformatted image in the coronal plane which reveals the transport system of the lungs.

The second image is a surface rendering of the lungs which reveals the parenchymal component which functions as the gas exchange system. The tree like features of the lungs is exemplified by an infrastructure of dividing branches which subserve the leaves - in essence a tubular system serving the factories of gas exchange. Courtesy Ashley Davidoff MD 32634d02 32634b02The lungs are part of a larger system called the respiratory system.

The role of the lungs is to deliver ambient air (ventilation) to the alveoli and to act as the agent for gas exchange by contributing one layer of epithelium to the bilayered membrane, a double layer which serves as the ultimate interface for gas exchange. The primary role of the pulmonary arterial circulation is to transport blood to the alveolar interface (perfusion) and to also play a part in the exchange of carbon dioxide and oxygen by providing the second layer of the bilayered filter.

It is the homeostatic aim of the body to match the ventilation with the perfusion, in order to maintain uniform ventilation (V) to perfusion (Q) ratio (V/Q). The lungs are exposed directly to the air in the atmosphere and to the blood within the circulatory system.

Through the lungs the blood is therefore exposed to the atmosphere, which on the one hand contains life sustaining oxygen but on the other can present a hostile environment filled with microorganisms, industrial chemicals, and toxic fumes. Alveolus In this diagram a single alveolus is outlined with its surrounding arteriole, venule, and capillary network. The process at the alveolar end is a simple exchange. Life sustaining oxygen is received by the hemoglobin and toxic carbon dioxide is excreted.

Although this exchange occurs in the respiratory bronchioles alveolar ducts and alveolar sacs, the alveolus is the prime site of gaseous exchange. Image courtesy Ashley Davidoff MD 42438b03The lungs are made of expandable, sponge-like tissues. Their close proximity to the heart and circulatory system allows for rapid exchange of gases between the air and the circulatory system as noted above.

This function is easily accomplished during rest, where resting respiratory rate in an adult is about 12 breaths per minute and heart rate 72 beats per minute. During exercise the respiratory rate can increase to 40-50 breaths per minute and the heart rate, increasing in concert, can reach 180-200 per minute.

The interface of circulation with the respiratory system has to be sufficiently equipped to allow delivery, uptake, and exchange of gases at this accelerated pace. The key soldier in the exchange of oxygen is a complex protein called hemoglobin which lies in the red cell.

I imagine the hemoglobin molecule scurried by the forces of the right ventricle into the pulmonary circulation. As it enters the chambers of exchange, the open windows of the lungs herald the fresh air. Under basal conditions, the hemoglobin gnome can work at a leisurely pace filling his baskets with oxygen. Under exercise conditions he has to start working like crazy, grabbing molecules of oxygen and stacking these into his storage baskets, surrounded by an accelerated pace with gale-like air forces and flood-like blood conditions.

Hemoglobin is a remarkable molecule and can adapt its function to these extremes in physiology. Carbon dioxide from bodily metabolism is dissolved in the blood. Exchanges between the circulation and alveoli occur rapidly and efficiently across the alveolar membrane due to differences in the partial pressure of gas between the blood and the alveoli.

The presence of a structure in the body that is almost totally filled with air makes it a unique, challenging, and rewarding organ to examine clinically and radiologically.

Examination of the lungs with a stethoscope enables the clinician to evaluate inspiratory and expiratory movement of air. Some pathologic conditions, including aspiration of a foreign body, collapsed lung, or inadvertent intubation of the bronchus, result in airway obstruction. In these conditions there is no air entry into the affected bronchus and subtended lung. The clinical finding of the lack of air entry, based simply on the lack of air sound, can be a life saving diagnostic maneuver.

Unusual but interesting words are used to describe the sounds of air character and movement on clinical examination.

These include percussion, tactile fremitus, bronchophony, whispering pectoriloquy, and egophony and relate to the wayair moves through the airways, and how the transmission may change when there is fluid in the pleural space or in the lungs. When the air mixes with the fluid, characteristic sounds such as rales and crepitus will result. Chest of Fruit This ""Chest of Fruit"" with the red pepper for the heart and clusters of grape-like oversized alveoli speaks for itself – The image provides a brief respite from the serious depths of our discussion about odd sounding terms for odd sounding breath sounds. Davidoff, M. D. "