lecture 26 Flashcards
what is air composed of?
78% N2,
21% O2,
0.033% CO2
Dalton’s Law definition
the total pressure exerted by a mixture of gases is the sum of pressures exerted by all individual gases
partial pressure
the pressure exerted by an individual gas
total air pressure, Patm= …. (all gases)
Pn2+ Po2 + Pco2
in humid air, Patm= … (all gases)
Pn2+ Po2+ Pco2 +Ph2o
in dry air Pgas= Patm*…
Patm*% of gas in atmosphere
in humid air, Pgas= (Patm…)*…
(Patm-Ph2o)*% gas in atmosphere
as alveolar ventilation increases, — increases and — decreases
Po2 increases and Pco2 decreases
in the atmosphere, Po2=?
160 mm Hg
in the atmosphere, Pco2=?
0.25 mm Hg
in the alveoli, Po2=?
(normal quiet breathing)
100 mm Hg
in the alveoli, Pco2=?
(normal quiet breathing)
40 mm Hg
alveolar partial pressures can vary with..
hypoventilation or hyperventilation
match perfusion with ventilation (explain)
perfusion= blood flow through organs and tissues
ventilation= breathing
the rate is matched, v efficient system
100 mm Hg in alveoli= 100 mm Hg in capillary blood
if you hypoventilate… (Po2 and Pco2)
v slow brething
Pco2 rises in alveoli
Po2 falls off
if you hyperventilate… (Po2 and Pco2)
v fast breathing
Pco2 falls off because you keep expelling it
Po2 rises because you keep pulling in o2
How does O2 enter alveoli/circulation?
-at a thin interface
-type I alveolar cells are for exchange
- O2 transported to heart
(98% attached to Hb in RBC, rest dissolved gas in plasma)
- O2 dropped of and used for cell resp.
what happens after O2 is used for cell resp. (byproduct?)
- used to create ATP.
- a byproduct of cell resp is CO2
- Co2 is transported as bicarbonate (HCO3-) or dissolved + bound to Hb
- CO2 is dropped in the lungs and expelled
What cellular barriers to O2 and CO2 have to diffuse across?
alveolar epithelial cells and capillary endothelial cells
(2 cells, 4 membranes)
-apical and basolateral membranes
Fick’s Law
greatest flux= high concentration (partial pressure) gradient
big distance= lower flux
–> diffusion rate proportional to: ADdeltaP/T^2
small change in T (thickness)= really big change in rate
rate of diffusion is directly proportional to (3 things)
- surface area (A)
- membrane permeability (D= diffusion constant)
- concentration (partial pressure) gradient
rate of diffusion is inversely proportional to
diffusion distance (T)
what is T in Fick’s Law?
diffusion distance
- membrane thickness
- interstitial fluid
what patterns does air follow in terms of flow between atmosphere and alveoli?
air moves by bulk flow between atmosphere and alveoli