Describe the site of gaseous exchange in human

Describe the site of gaseous exchange in human

Gaseous exchange surface in man is composed of alveoli in the  lungs

–  the alveolus is a single celled air bag with intimate association with blood capillaries

Adaptation of alveoli for gaseous exchange

• They are very numerous that they offer a big surface area for gaseous exchange
• Alveolar epithelium is covered internally with a thin layer of fluids in which oxygen dissolves before diffusing into the blood which create high diffusion gradient.
• Alveolar fluid contains surfactants that prevent alveolar form collapsing
• Alveolus is separated form blood capillaries by thin membrane that offer minimum resistance to diffusion of gases.
• The blood capillaries of the alveolus are smaller than the red blood cells such that when cell squeeze through the capillaries, they make intimate contact with capillary membranes that ease gaseous diffusion.

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