- Human lung
Name = PAGENAME
Latin = pulmo
GraySubject = 240
GrayPage = 1093
Caption = Frontal view of lungs cut open
Trachea branches into bronchi
MeshName = Lung
MeshNumber = A04.411
The human lungs are the human organs of respiration.
Humans have two
lungs, with the left being divided into two lobes and the right into three lobes. Together, the lungs contain approximately 1500 miles (2,400 km) of airways and 300 to 500 million alveoli, having a total surface area of about 70 m2 in adults — roughly the same area as a badmitoncourt. [cite book |author=Notter, Robert H. |title=Lung surfactants: basic science and clinical applications |publisher=Marcel Dekker |location=New York, N.Y |year=2000 |pages=120 |isbn=0-8247-0401-0 |oclc= |url=http://books.google.com/books?id=pAuiWvNHwZcC&pg=PA120&lpg=PA120&dq=area+tennis+court+alveoli&source=web&ots=npC4gsCknM&sig=VJDxOB_U246erlV_uXHjXS3yzow&hl=en&sa=X&oi=book_result&resnum=3&ct=result |accessdate=2008-10-11] Furthermore, if all of the capillaries that surround the alveoli were unwound and laid end to end, they would extend for about 620 miles.
* The conducting zone contains the trachea, the
bronchi, the bronchioles, and the terminal bronchioles
* The respiratory zone contains the
respiratory bronchioles, the alveolar ducts, and the alveoli.
The conducting zone and the respiratory zone (but not the alveoli) are made up of
The conducting zone has no gas exchange with the blood, and is reinforced with cartilage and smooth muscle, which are very strong. Smooth muscle has variable resistance to air flow. The conducting zone warms the air to 37 degrees Celsius and humidifies the air. It also cleanses the air by removing particles. Every time you breathe in and out your lungs are hard at work.Your lungs are surround by your rib cage.
The respiratory zone is the site of
gas exchangewith blood.
The smooth muscle tone in bronchioles, and therefore bronchiolar diameter, is controlled by:
sympathetic nervous systemvia noradrenalineacting on the beta receptorsand causes bronchodilation
parasympathetic nervous systemvia acetylcholinewhich acts on the M-1 muscarinic receptors and maintains the resting tone of the bronchiolar smooth muscle. This action is related, although considered distinct from bronchoconstriction
* many other non-autonomic nervous and biochemical stimuli including, for example,
intrapleural spaceis the potential space between the pleuralining the inner wall of the thoracic cage and the pleura lining the lungs.
Total lung capacity(TLC) includes inspiratory reserve volume, tidal volume, expiratory reserve volume, and residual volume.cite book | author = Weinberger SE | title = Principles of Pulmonary Medicine | edition = 4th ed.| publisher = Saunders | year = 2004 | id = ISBN 0-7216-9548-5 ] The total lung capacity depends on the person's age, height, weight, sex, and normally ranges between 4,000 and 6,000 cm3 (4 to 6 L). For example, females tend to have a 20–25% lower capacity than males. Tall people tend to have a larger total lung capacity than shorter people. Smokers have a lower capacity than nonsmokers. Lung capacity is also affected by altitude. People who are born and live at sea levelwill have a smaller lung capacity than people who spend their lives at a high altitude. In addition to the total lung capacity, one also measures the tidal volume, the volume breathed in with an average breath, which is about 500 cm3. For a detailed discussion of the various lung volumes, see the article on lung volumes. [cite book
last = Maton
first = Anthea
coauthors = Jean Hopkins, Charles William McLaughlin, Susan Johnson, Maryanna Quon Warner, David LaHart, Jill D. Wright
title = Human Biology and Health
publisher = Prentice Hall
date = 1993
location = Englewood Cliffs, New Jersey, USA
isbn = 0-13-981176-1]
Typical resting adult respiratory rates are 10–20 breaths per minute with 1/3 of the breath time in inspiration.
Human lungs are to a certain extent 'overbuilt' and have a tremendous reserve volume as compared to the oxygen exchange requirements when at rest. This is the reason that individuals can smoke for years without having a noticeable decrease in lung function while still or moving slowly; in situations like these only a small portion of the lungs are actually perfused with blood for gas exchange. As oxygen requirements increase due to
exercise, a greater volume of the lungs is perfused, allowing the body to reach its CO2/O2 exchange requirements.
Diseases of the human lung belong to
respiratory diseases. The following is a list of important medical conditions involving the lung. Many of these are caused or worsened by smoking.
Emphysemais an enlargement of the air spaces in the lung, making it hard to breathe.
Asthmais an immunological disease which causes the bronchioles to narrow by inflammation and spasm of the lining of the airway wall.
Cystic fibrosisis a hereditary diseasewhich causes the lung to produce abnormally viscous mucus.
pulmonary embolismoccurs when a blood clot obstructs an arteryleading to the lung.
Tuberculosisis a transmittable bacterial infection of the lung, the most common infectious disease today.
Pneumoniais an infection of the lung, caused by bacteria, viruses or fungi.
Pneumoconiosis, an occupational lung diseasecaused by the inhalationof dust.
Bronchitisis an inflammationof the bronchi.
collapsed lung(pneumothorax) can occur when one or both walls of the pleural cavity are penetrated by injury, allowing air to enter.
pulmonary edemafluid from the capillaries enters the alveoli. This can be caused by weakness of the left side of the heart (resulting in a blood holdup in the lung), altitude sickness, or rarely inhaling toxicgases.
Lung pinprick conditionis a hereditary diseasewhich results in decreased lung capacity and occasional shortness of breath.
Transplantation now allows for a person to have a single
lung transplant, a double-lung transplant, or a transplant of both the heart and lungs.
Modification of substances
The lungs convert
angiotensin Ito angiotensin II. In addition, they remove several blood-bourne substances, e.g. PGE1, PGE2, PGF2α, leukotrienes, serotonin, bradykinin. cite book |author=Walter F., PhD. Boron |title=Medical Physiology: A Cellular And Molecular Approaoch |publisher=Elsevier/Saunders |location= |year=2004 |pages= |isbn=1-4160-2328-3 |oclc= |doi= |accessdate= Page 605 ]
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