Transcript Partial Pressures of O2 and CO2

Partial Pressures of
O2 and CO2
 Normal air pressure at sea level
760 mm Hg = 1 atm = 101.3 kPa
PO2
PCO
2
PH2
O
PN2
P
total
air
trachea
alveoli
artery
vein
159.6
149.2
104.0
100.0
40.0
000.3
000.3
040.0
040.0
46.0
000.0
047.0
047.0
047.0
47.0
600.1
563.5
569.0
569.0
569.0
760.0
760.0
760.0
756.0
706.0
Gas Exchange in Alveoli
 Alveolar Capillaries
(Blood traveling from heart to lung – deoxygenated
blood)
 diffusion
of oxygen from the alveoli into the
blood
 diffusion of carbon dioxide from the blood
into the alveoli.
Gas Exchange in Alveoli
 PO2 = 40 mm Hg
relatively low because this blood has just
returned from the systemic circulation & has
lost much of its oxygen
 PCO2 = 45 mm Hg
relatively high because the blood returning
from the systemic circulation has picked up
carbon dioxide
Pressure in the Lungs
Gas Exchange in the Tissue
 Blood leaving the alveolar capillaries
returns heart and is pumped into the
systemic circulation.
 This blood travels through arteries and
arterioles and finally capillaries where
gas exchange with the surrounding
tissue occurs.
Gas Exchange in the Tissue
Gas Exchange in the Tissue
 Entering the systemic capillaries
 PO2
= 100 mm Hg
 PCO2 = 40 mm Hg
 Body cells (resting conditions)
 PO2
= 40 mm Hg
 PCO2 = 45 mm Hg
Gas Exchange in the Tissue
 Differences in partial pressures of
oxygen & carbon dioxide in the systemic
capillaries & the body cells cause:

oxygen to diffuse from the blood & into the
cells
 carbon dioxide to diffuse from the cells into
the blood.
Gas Exchange in the Tissue
 Leaving the systemic capillaries
 PO2
= 40 mm Hg
 PCO2 = 45 mm Hg
 Blood leaving the systemic capillaries
returns to the heart and is then pumped
to the lungs to repeat the process
Review