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The width of the chest during inspiration
A) Decreases
B) Does not changes
C) Increases
D) None of these

Last updated date: 20th Jun 2024
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Hint:Inspiration is an active process, which occurs due to contraction of inspiratory muscles, whereas normal expiration is a passive phenomenon that occurs due to elastic recoil of the lungs. Main muscles for inspiration process: diaphragm and external intercostal muscle.

Complete answer:
Processes of breathing are relaxing, inspiration, expiration. Mechanism of breathing: Contraction of inspiratory muscles expands the thoracic cavity that leads to decreased intrapleural pressure. Drop in intrapleural pressure aids the lungs to expand. Expansion of lungs decreases intrapulmonary pressure to sub atmospheric level due to which air from the atmosphere is sucked into lungs. Expiration is the process of return of ribs to rest position causes diminishing of lung volume. Return of diaphragm to rest position also leads to diminish of lung volume. Diminishing lung volume causes pressure in the lung to increase to a higher value than atmospheric pressure. Air flows out of lungs.

When you breathe in or inhale, your diaphragm constricts and moves downward. This process increases the space in the chest cavity into which lungs will expand. The intercostal muscles between ribs help augment the chest cavity.

Thus, the correct answer is option (B).

Note:Muscles for expiration are internal intercostal, pectoral, abdominal muscles. Relax state is diaphragm and intercostal muscles relaxed. Inspiration process is an active process. Expiration process is a passive process. Diaphragm is responsible for about 75% of respiration. Respiratory muscle is diaphragm, intercostal muscles.