cgier 28 Flashcards
The gases in the alveoli come into equilibrium with the blood by — across the —– and —–
- diffusion ( from difference in partial pressure between the alveoli and the blood )
- pulmonary epithelium and capillary walls
The pressure exerted by an individual gas in a mixture is known as its
partial pressure
at — level the —- typically supports column mercury 760nm high
- sea level
- barometric pressure
oxygen’s share of that pressure can be calculated as:
Air = 760mm Hg, Oxygen 21% in Air 0.21 X 760 = 160mm Hg
( since oxygen makes up 21%)
and co2 can be done similarly ( 0.004% x 760 )
*Fick’s law of diffusion states ,The amount of oxygen or carbon dioxide that diffuses across the membrane of an alveolus depends on the
-differences in partial pressure on the two sides of the membrane & on the surface area of the membrane.
- gas diffuses faster if the difference in pressure or surface area increases
- rate of diffusion = K x A x ( p2-p1 / d)
k: diffusion constant
a : area
d: distance
p: difference in pp
There is a gradient of PO2 from dry inspired air to alveolar air, from 160 to 104 due to
due to an increase in partial pressure of water vapour
O2 present in blood in two forms:
1- physical : dissolved in the plasma
2- chemical combination: >98 bound to haemoglobin in the blood
O2 in arterial blood — and in tissues ( at rest )
- 100 mm hg
- 40 mm hg
-Oxygen diffuses out of the —– and into the tissues.
capillaries
When arterial blood reaches tissue capillaries, the gradient is
reversed
-Because PO2 is lower in the cells, oxygen diffuses the pressure gradient into the cells. Returning venous blood will now have the same PO2 as the cells it just passed.
02 has poor solubiltiy in the — which is insufficient
- blood
- so the remaining 98% will combine reversely w/ haemoglobin and increases the 02 transport
-Blood contains a large concentration of haemoglobin (140 - 180 g/L for men, 120 to 160 g/L for women)
each haemoglobin molicule can bind to — o2 molecules and — % of 02 in the blood is bounded to heamoglobin
- 4 02 molecules
- 89.5%
when the oxygen concentration increases , there is a — in binding to haemoglobin and its highest in
increase , pulmonary capillaries
in the OXYGEN-HAEMOGLOBIN DISSOCIATION CURVE the relationship is not linear but is
- sigmoid due to the cooperative binding of 02 to haemoglobin
maximum amount of oxygen that haemoglobin can transport is
Oxygen-carrying capacity