ANIMAL PHYSIOLOGY
GAS EXCHANGE IN HUMANS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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The thickness of the single-cell layer of alveoli membranes
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The secretion of fluids in the inner surface of the alveoli
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The pressure within the thoracic cavity
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The dense net of capillaries covering the alveoli
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Detailed explanation-1: -Surfactant is released from the lung cells and spreads across the tissue that surrounds alveoli. This substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy.
Detailed explanation-2: -Special cells in the walls of the alveoli secrete a film of fatty substances called surfactant . This substance prevents the alveolar walls from collapsing and sticking together when air is expelled.
Detailed explanation-3: -It is established that pulmonary surfactant reduces surface tension at the air–water interface in the alveoli, thereby preventing collapse of these structures at end-expiration. In this manner, surfactant reduces the work associated with breathing.
Detailed explanation-4: -The surfactant lines the alveolar walls over the water film, and then reduces the surface tension and thus the collapsing pressure.
Detailed explanation-5: -Type II pneumocytes secrete fluid that lines the inside of the alveolus. The fluid contains a surfactant. Surfactants are amphipathic (they have hydrophobic and hydrophilic regions). They reduce surface tension and prevent the walls of the alveoli from sticking together.