Gas Exchange

Dalton’s law of partial pressure

In a mixture of gases, each gas exerts its own pressure = partial pressure

Total gas pressure

Sum of all individual pressure

Total atmospheric pressure

PN2 + PO2 + P other gases = 760 mmHg

Partial pressure of each gas

PO2 = 159mmHg
PN2 = 597mmHg
PCO2 = 0.3mmHg
PH2O = 3.8mmHg
Trace amounts of noble gases

Composition of inhaled air

159mmHg oxygen, 3.7mmHg water, 0.3mm carbon dixoide

Composition of exhaled air

104mmHg oxygen, 47mmHg water, 40mmHg carbon dioxide

Structural functional relationship for gas exchange

Thin respiratory membrane - squamous epithelium of alveolus and capillaries for diffusion, each alveolus covered with pulmonary capillaries to keep diffusion distance short, oxygen and carbon dioxide are lipid soluble and can diffuse through cell membrane, total surface are for diffusion is large