السؤال 20

During a quiet breath in, the diaphragm, a sheet of muscle below the lungs, contracts. What happens next?

Chest volume falls and air enters.
The trachea closes while air enters.
Chest volume stays fixed and air is pumped by alveoli.
Chest volume rises and air moves inward.الإجابة الصحيحة

الشرح

Diaphragm contraction increases the volume of the chest, lowering pressure relative to the outside and drawing air inward. Forcing air out is associated with decreasing chest volume, not this downward contraction during quiet inhalation.

الشرح

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