Lung

The lungs are the primary <a href="/facts/Organ_(biology)/FUYsLaxz">organs</a> of the <a href="/facts/Respiratory_system/IG8v5JEr">respiratory system</a> in many animals, including humans. In <a href="/facts/Mammal/phSwTzBo">mammals</a> and most other <a href="/facts/Tetrapod/vWpAxzAW">tetrapods</a>, two lungs are located near the <a href="/facts/Vertebral_column/Nuw1kV7o">backbone</a> on either side of the <a href="/facts/Heart/fF4KSGdk">heart</a>. Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of <a href="/facts/Gas_exchange/3vUewPNH">gas exchange</a>. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their musculoskeletal systems to support and foster breathing. In early tetrapods, air was driven into the lungs by the pharyngeal muscles via <a href="/facts/Buccal_pumping/mNfT11AU">buccal pumping</a>, a mechanism still seen in amphibians. In humans, the primary muscle that drives breathing is the <a href="/facts/Thoracic_diaphragm/aw7KcUou">diaphragm</a>. The lungs also provide airflow that makes <a href="/facts/Animal_communication/nHBjVw3c">vocalisation</a> including <a href="/facts/Speech/WEelhfTs">speech</a> possible.
Humans have two lungs, a right lung and a left lung. They are situated within the thoracic cavity of the <a href="/facts/Chest/lwtzfc8K">chest</a>. The right lung is bigger than the left, and the left lung shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the <a href="/facts/Lower_respiratory_tract/nnG9UEmr">lower respiratory tract</a> that begins at the <a href="/facts/Trachea/zMSEwjAy">trachea</a> and branches into the <a href="/facts/Bronchi/t83cUXou">bronchi</a> and <a href="/facts/Bronchiole/2mPRrpQs">bronchioles</a>, which receive air <a href="/facts/Inhalation/eB5VlguF">breathed in</a> via the <a href="/facts/Conducting_zone/nnG9UEmr">conducting zone</a>. These divide until air reaches microscopic <a href="/facts/Pulmonary_alveolus/aEHP1ATT">alveoli</a>, where gas exchange takes place. Together, the lungs contain approximately 2,400 kilometers (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within a <a href="/facts/Pleural_sac/Wel4Tz7p">pleural sac</a> of two <a href="/facts/Pleurae/Wel4Tz7p">pleurae</a> which allows the inner and outer walls to slide over each other whilst breathing takes place, without much friction. The inner <a href="/facts/Visceral_pleura/A5E7jwNe">visceral pleura</a> divides each lung as fissures into sections called lobes. The right lung has three lobes and the left has two. The lobes are further divided into <a href="/facts/Bronchopulmonary_segment/6EES1Y5j">bronchopulmonary segments</a> and lobules. The lungs have a unique blood supply, receiving deoxygenated blood sent from the heart to receive oxygen (the <a href="/facts/Pulmonary_circulation/mBM1zMzc">pulmonary circulation</a>) and a separate supply of oxygenated blood (the <a href="/facts/Bronchial_circulation/zhny41uX">bronchial circulation</a>).
The tissue of the lungs can be affected by several <a href="/facts/Respiratory_disease/CDRTg5Ev">respiratory diseases</a> including <a href="/facts/Pneumonia/Jw0KquTA">pneumonia</a> and <a href="/facts/Lung_cancer/LHLdR454">lung cancer</a>. Chronic diseases such as <a href="/facts/Chronic_obstructive_pulmonary_disease/ud3oXGCr">chronic obstructive pulmonary disease</a> and <a href="/facts/Emphysema/ud3oXGCr">emphysema</a> can be related to smoking or exposure to harmful substances. Diseases such as bronchitis can also affect the respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων "lung") as in pneumonia.
In <a href="/facts/Embryonic_development/1lFY4EoW">embryonic development</a>, the lungs begin to develop as an outpouching of the <a href="/facts/Foregut/ngnGu9bV">foregut</a>, a tube which goes on to form the upper part of the <a href="/facts/Digestive_system/SdpF0sWq">digestive system</a>. When the lungs are formed the <a href="/facts/Fetus/evocHd0Y">fetus</a> is held in the fluid-filled <a href="/facts/Amniotic_sac/KatPHMhg">amniotic sac</a> and so they do not function to breathe. Blood is also diverted from the lungs through the <a href="/facts/Ductus_arteriosus/7eBnYRSx">ductus arteriosus</a>. <a href="/facts/Adaptation_to_extrauterine_life/tdbooAVn">At birth</a> however, air begins to pass through the lungs, and the diversionary duct closes so that the lungs can begin to respire. The lungs only fully develop in early childhood.

Lung open-in-new

Lung