View source for Alveolar-capillary barrier

{{Infobox Anatomy |
  Name         = {{PAGENAME}} |
  Latin        = |
  GraySubject  = |
  GrayPage     = |
  Image        = Alveoli.svg  |
  Caption      = Gaseous exchange in the lung. |
  Image2       = |
  Caption2     = |
  Precursor    = |
  System       = |
  Artery       = |
  Vein         = |
  Nerve        = |
  Lymph        = |
  MeshName     = Blood-Air+Barrier |
  MeshNumber   = A04.411.715.025 |
  DorlandsPre  = m_08 |
  DorlandsSuf  = 12522385  |
}}
{{SI}}
{{CMG}}



==Overview==
The '''alveolar-capillary barrier''' (or '''membrane''', or '''blood-air barrier''') exists in the gas exchanging region of the [[lungs]].  It exists to prevent air bubbles from forming in the blood, and from blood entering the alveoli. It is formed by the type 1 [[pneumocytes]] of the alveolar wall, the [[endothelial]] cells of the [[capillaries]] and the [[basement membrane]] between the two cells.  The barrier is [[Vascular permeability|permeable]] to molecular [[oxygen]], [[carbon dioxide]], [[carbon monoxide]] and many other gases.<ref>{{citebook|title=Physiology for Health Care and Nursing|author= Sheenan Kindlen|yeat=2003|publisher=Elsevier Health Sciences| pages=130|id=ISBN 0443071160|url=http://books.google.com/books?id=UmPzgwVbnBoC&pg=PA130&ots=-5bFL4pqz_&dq=%22Alveolar-capillary+barrier%22&as_brr=3&ei=Hqa8RtieNIXy6gKu1KjEBQ&ie=ISO-8859-1&output=html&sig=MWd03S-rw3zcC2KirZWc1Zwmwbc}}</ref>
 
This blood gas barrier is extremely thin (600-800 nm; some places merely 200 nm) so as to allow sufficient oxygen diffusion, yet it is extremely strong. This strength comes from the [[type 4 collagen]] in between the [[endothelial]] and [[epithelial]] cells. Damage can occur to this barrier at pressures of around 40mmhg. Failure of the barrier is often seen in racehorses and other domesticated horses due to exercise induced blood pressure rising above normal.

==See also==
* [[Pulmonary vein]]

==References==
{{refs}}

==External links==
* {{UCDavisOrganology|Respiratory/lung/vasc4/vasc}} - "Mammal, lung vasculature (EM, High)"
* {{EmbryologySwiss|rrespiratory/phasen05}}

{{Lung}}


[[Category:Respiratory system]]
[[Category:Anatomy]]
[[Category:Pulmonology]]

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