PHYS20008 Lecture Notes - Lecture 21: Pressure Gradient, Carbonic Anhydrase, Extracellular Fluid
10 May 2018
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Lecture 21
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- Alveoli surrounded by elastic fibres and capillaries
- Alveoli: very thin, a lot of exchange, no smooth muscles, thin layer of cells around
outside of alveoli, elastic fibres for recoil (elastance within lungs), dense rich network
of capillaries surrounding alveoli (get gases in and out of bloodstream)
- Elastic fibres break down in emphysema → hard to deflate lungs properly
- Bronchioles have smooth muscles
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- Type 1 alveolar cell: very thin for gas exchange
- Type 2 alveolar cell: surfactant releasing cells to break down surface tension of water
lining surface of alveoli
- Smaller alveoli will have higher proportion of type 2 cells than large ones do because
of law of LaPlace that says that smaller ones are more difficult to inflate than large
ones
- Very thin layer of interstitial fluid between capillaries and alveolar cells, where gas
exchange happens
- Alveolar macrophage: ingest foreign material that comes in, protects us from all kinds
of bad things from environment that we inhale in
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- Maintain thin interstitial space between capillary and alveolus
- Pulmonary oedema: build up of fluid in interstitial space → challenging for gas
diffusion (Fick’s Law: thicker membrane lower rate of diffusion)
- Well-oxygenated blood is carried by aorta and pulmonary vein
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- Pulmonary blood pressure much lower than systemic blood pressure: doesn’t need to
be that high because circuit is quite short (don’t need as much pressure to overcome
resistance); level of interstitial fluid, Starling forces, increase hydrostatic forces in the
system → need more filtration, more fluid moving out of vessels → build up of fluid in
interstitial space → bad for gas exchange, want to keep pressure low
find more resources at oneclass.com
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Document Summary
Alveoli surrounded by elastic fibres and capillaries. Elastic fibres break down in emphysema hard to deflate lungs properly. Type 1 alveolar cell: very thin for gas exchange. Type 2 alveolar cell: surfactant releasing cells to break down surface tension of water lining surface of alveoli. Smaller alveoli will have higher proportion of type 2 cells than large ones do because of law of laplace that says that smaller ones are more difficult to inflate than large ones. Very thin layer of interstitial fluid between capillaries and alveolar cells, where gas exchange happens. Alveolar macrophage: ingest foreign material that comes in, protects us from all kinds of bad things from environment that we inhale in. Maintain thin interstitial space between capillary and alveolus. Pulmonary oedema: build up of fluid in interstitial space challenging for gas diffusion (fick"s law: thicker membrane lower rate of diffusion) Well-oxygenated blood is carried by aorta and pulmonary vein.
