Question

During inspiration, as a result of contraction of muscles attached to it, the diaphragm
A. Becomes dome-shaped
B. Flattens
C. Rotates
D. Flattens and rotates

Answer 1

Hint:-Inspiration and expiration are the two steps of breathing. Inspiration is an active process in which atmospheric air is taken into the lungs. Expiration is the passive process in which air from the lung is expelled out into the atmosphere. The uptake of air into lungs and expulsion of air from the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere.

Complete Answer:-
Diaphragm is the primary respiratory muscle which is the skeletal muscle separating the thoracic cavity from abdominal cavity. The diaphragm along with the internal and external intercostal muscles helps in the formation of a pressure gradient between the atmosphere and pulmonary cavity. In a normal relaxed state, the diaphragm has a dome-shaped position.
Inspiration is initiated by the contraction of diaphragm. Their contraction flattens the diaphragm from its dome shape, increasing the volume of the thoracic cavity. The muscles associated with diaphragm, phrenic nerve muscles, extend from the diaphragm to ribs to the vertebral column.
There are 11 pairs of muscles between the 12 pairs of ribs. They are the intercostal muscles. During inspiration, the internal and external intercostal muscles contract. Their contraction raises the ribs and the sternum and the thoracic volume increases. As the volume of thoracic cavity increases, the volume of intrapulmonary cavity increases and intrapulmonary pressure decreases than atmospheric pressure. Thus inspiration occurs. The contraction of diaphragm along with intercostal muscles facilitates inspiration.
Diaphragm attains dome shape by relaxation which happens during expiration, the release of air from lungs to the atmosphere.
Thus, the right option is B.

Note:- Expiration or exhalation is a passive process which involves the relaxation of diaphragm and external intercostal muscles which returns the diaphragm, sternum and ribs into their normal position thereby reducing the volume of the thoracic cavity. The decrease in the volume of thoracic cavity decreases the intrapulmonary volume and increases the intrapulmonary pressure than the atmospheric pressure. Thus, expiration occurs.