Human lung
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Reverted edits by [[Special:Contributions/220.237.152.154|220.237.152.154]] to last version by Intelliagent (using [[WP:HG|Huggle]])
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Caption = Frontal view of lungs cut open<br />Trachea branches into bronchi |
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The '''human lungs''' are the human organs of [[Respiration (physiology)|respiration]].
Humans have two [[lung]]s, 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 75 m<sup>2</sup> in adults — roughly the same area as a [[tennis court]].<ref name=Rhoades_2003>{{cite book | author = Rhoades RA, Tanner GA (editors) | title = Medical Physiology | edition = 2nd ed.| publisher = Lippincott Williams & Wilkins | year = 2003 | id = ISBN 0-7817-1936-4 }}</ref> Furthermore, if all of the capillaries that surround the alveoli were unwound and laid end to end, they would extend for about 620 miles.
==Organization==
*The conducting zone contains the [[Vertebrate trachea|trachea]], the [[bronchi]], the [[bronchiole]]s, and the [[terminal bronchioles]]
*The respiratory zone contains the [[respiratory bronchiole]]s, the [[alveolar duct]]s, and the [[alveoli]].
The conducting zone and the respiratory zone (but not the alveoli) are made up of [[airway]]s.
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.
The respiratory zone is the site of [[gas exchange]] with blood.
The smooth muscle tone in bronchioles, and therefore bronchiolar diameter, is controlled by:
*the [[sympathetic nervous system]] via [[noradrenaline]] acting on the [[beta receptors]] and causes [[bronchodilation]]
*the [[parasympathetic nervous system]] via [[acetylcholine]] which acts on the [[muscarinic receptor]]s and causes [[bronchoconstriction]]
*many other non-autonomic nervous and biochemical stimuli including, for example, [[carbon dioxide]].
The [[intrapleural space]] is the potential space between the [[pleura]] lining the inner wall of the thoracic cage and the pleura lining the lungs.
==Physiology==
[[Total lung capacity]] (TLC) includes [[inspiratory reserve volume]], [[tidal volume]], [[expiratory reserve volume]], and [[residual volume]].<ref name=Weinberger_2004>{{cite book | author = Weinberger SE | title = Principles of Pulmonary Medicine | edition = 4th ed.| publisher = Saunders | year = 2004 | id = ISBN 0-7216-9548-5 }}</ref> The total lung capacity depends on the person's age, height, weight, sex, and normally ranges between 4,000 and 6,000 cm<sup>3</sup> (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. [[tobacco smoking|Smokers]] have a lower capacity than nonsmokers. Lung capacity is also affected by altitude. People who are born and live at [[sea level]] will 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 cm<sup>3</sup>. For a detailed discussion of the various lung volumes, see the article on [[lung volumes]].<ref>{{cite book
| last = Maton
| first = Anthea
| authorlink =
| 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
| pages =
| url =
| doi =
| id =
| isbn = 0-13-981176-1}}</ref>
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 [[Carbon Dioxide|CO<sub>2</sub>]]/[[Oxygen|O<sub>2</sub>]] exchange requirements.
==Diseases==
Diseases of the human lung belong to [[respiratory disease]]s. The following is a list of important medical conditions involving the lung. Many of these are caused or worsened by [[tobacco smoking|smoking]].
* [[Lung cancer]]
* [[Emphysema]] is an enlargement of the air spaces in the lung, making it hard to breathe.
* [[Asthma]] is an immunological disease which causes the bronchioles to narrow by inflammation and spasm of the lining of the airway wall.
* [[Cystic fibrosis]] is a [[hereditary disease]] which causes the lung to produce abnormally viscous [[mucus]].
* A [[pulmonary embolism]] occurs when a blood clot obstructs an [[artery]] leading to the lung.
* [[Tuberculosis]] is a transmittable bacterial infection of the lung, the most common infectious disease today.
* [[Pneumonia]] is an infection of the lung, caused by [[bacterium|bacteria]], [[virus]]es or [[fungus|fungi]].
* [[Pneumoconiosis]], an [[occupational lung disease]] caused by the [[inhalation]] of dust.
* [[Bronchitis]] is an [[inflammation]] of the bronchi.
* A [[collapsed lung]] (pneumothorax) can occur when one or both walls of the pleural cavity are penetrated by injury, allowing air to enter.
* In [[pulmonary edema]] fluid 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 [[toxic]] gases.
* [[Lung pinprick condition]] is a [[hereditary disease]] which 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-lung transplant|heart and lungs]].
== Modification of substances==
The lungs convert [[angiotensin I]] to [[angiotensin II]]. In addition, they remove several [[blood]]-bourne substances, e.g. [[PGE1|PGE<sub>1</sub>]], [[PGE2|PGE<sub>2</sub>]], [[PGF2alpha|PGF<sub>2α</sub>]], [[leukotrienes]], [[serotonin]], [[bradykinin]]. <ref name=boron> {{cite book |author=Walter F., PhD. Boron |title=Medical Physiology: A Cellular And Molecular Approaoch |publisher=Elsevier/Saunders |location= |year= |pages= |isbn=1-4160-2328-3 |oclc= |doi=}} Page 605 </ref>
==References==
{{reflist}}
==Additional images==
<gallery>
Image:Lungs_diagram_detailed.svg|Detailed diagram of the lungs
Image:Illu_bronchi_lungs.jpg|[[Bronchi]], bronchial tree, and [[lungs]].
</gallery>
{{Respiratory_system}}
{{cardiovascular_system}}
{{Lung}}
[[Category:Respiratory system]]
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