Pulmonary alveolus

Pulmonary alveolus
Pulmonary alveolus
	The alveoli
Details
System	Respiratory system
Location	Lung
Identifiers
Latin	alveolus pulmonis
MeSH	D011650
TH	H3.05.02.0.00026
FMA	7318
	Anatomical terminology

A pulmonary alveolus (pl.: alveoli, from Latin alveolus, "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where pulmonary gas exchange takes place.^[1] Oxygen is exchanged for carbon dioxide at the blood–air barrier between the alveolar air and the pulmonary capillary.^[2] Alveoli make up the functional tissue of the mammalian lungs known as the lung parenchyma, which takes up 90 percent of the total lung volume.^[3]^[4]

Alveoli are first located in the respiratory bronchioles that mark the beginning of the respiratory zone. They are located sparsely in these bronchioles, line the walls of the alveolar ducts, and are more numerous in the blind-ended alveolar sacs.^[5] The acini are the basic units of respiration, with gas exchange taking place in all the alveoli present.^[6] The alveolar membrane is the gas exchange surface, surrounded by a network of capillaries. Oxygen is diffused across the membrane into the capillaries and carbon dioxide is released from the capillaries into the alveoli to be breathed out.^[7]^[8]

Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates.^[9]

^ "Pulmonary Gas Exchange - MeSH - NCBI". www.ncbi.nlm.nih.gov. Retrieved 30 December 2022.
^ "Alveoli". www.cancer.gov. 2 February 2011. Retrieved 22 July 2021.
^ Cite error: The named reference Knudsen was invoked but never defined (see the help page).
^ Jones, Jeremy. "Lung parenchyma | Radiology Reference Article | Radiopaedia.org". Radiopaedia. Retrieved 15 August 2021.
^ Cite error: The named reference Moore was invoked but never defined (see the help page).
^ Hansen JE, Ampaya EP, Bryant GH, Navin JJ (June 1975). "Branching pattern of airways and air spaces of a single human terminal bronchiole". Journal of Applied Physiology. 38 (6): 983–9. doi:10.1152/jappl.1975.38.6.983. PMID 1141138.
^ Hogan CM (2011). "Respiration". In McGinley M, Cleveland CJ (eds.). Encyclopedia of Earth. Washington, D.C.: National council for Science and the Environment.
^ Paxton S, Peckham M, Knibbs A (2003). "Functions of the Respiratory Portion". The Leeds Histology Guide. Faculty of Biological Sciences, University of Leeds.
^ Daniels CB, Orgeig S (August 2003). "Pulmonary surfactant: the key to the evolution of air breathing". News in Physiological Sciences. 18 (4): 151–7. doi:10.1152/nips.01438.2003. PMID 12869615.

[MeSH1-1] "Pulmonary Gas Exchange - MeSH - NCBI". www.ncbi.nlm.nih.gov. Retrieved 30 December 2022.

[SEER-2] "Alveoli". www.cancer.gov. 2 February 2011. Retrieved 22 July 2021.

[Knudsen-3] Cite error: The named reference Knudsen was invoked but never defined (see the help page).

[Jones-4] Jones, Jeremy. "Lung parenchyma | Radiology Reference Article | Radiopaedia.org". Radiopaedia. Retrieved 15 August 2021.

[Moore-5] Cite error: The named reference Moore was invoked but never defined (see the help page).

[6] Hansen JE, Ampaya EP, Bryant GH, Navin JJ (June 1975). "Branching pattern of airways and air spaces of a single human terminal bronchiole". Journal of Applied Physiology. 38 (6): 983–9. doi:10.1152/jappl.1975.38.6.983. PMID 1141138.

[7] Hogan CM (2011). "Respiration". In McGinley M, Cleveland CJ (eds.). Encyclopedia of Earth. Washington, D.C.: National council for Science and the Environment.

[8] Paxton S, Peckham M, Knibbs A (2003). "Functions of the Respiratory Portion". The Leeds Histology Guide. Faculty of Biological Sciences, University of Leeds.

[9] Daniels CB, Orgeig S (August 2003). "Pulmonary surfactant: the key to the evolution of air breathing". News in Physiological Sciences. 18 (4): 151–7. doi:10.1152/nips.01438.2003. PMID 12869615.

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]