Question

when you are breathing gently, expiration results from which of the following?
a contraction of muscles in the chest
b contraction of the diaphragm
c elastic recoil of the tissues
d high pressure in the lungs

Explanation:

During gentle breathing (eupnea), expiration is a passive process. The diaphragm relaxes (not contracts as in B), and the muscles in the chest (A) are not contracting for expiration in normal gentle breathing. High - pressure in the lungs (D) is a result of the elastic recoil of tissues (C) rather than the cause. The elastic recoil of the lung tissues and the thoracic cage causes the volume of the thoracic cavity to decrease, increasing the intrapulmonary pressure relative to the atmospheric pressure, and air is forced out.

Answer:

C. Elastic recoil of the tissues