Question

When the diaphragm contracts, _______. A. it lifts the rib cage B. it flattens out C. it flattens out and D. it rises in the thoracic cavity E. it rises in the thoracic cavity

Answer 1

It flattens out

Step-by-step explanation:

The diaphragm is a dome-shaped think skeletal muscle present in the thoracic cavity which separates the chest cavity from the abdomen.

Diaphragm along with intercostal muscles regulates the mechanism of breathing. When the diaphragm contracts, the muscle fattens which causes the rib cage to expand thus increase the volume for inspiration while when it relaxes, it uplifts the rib cage and causes exhalation.

Thus, it flattens out is the correct answer.

Answer 2

The given question is incorrect. The correct question is:

Question: When the diaphragm contracts, _______.

A) it lifts the rib cage

B) it rises in the thoracic cavity

C) it flattens out

D) it flattens out and it rises in the thoracic cavity

Answer:

C) it flattens out

Step-by-step explanation:

The diaphragm is a muscular dome-shaped structure. It contracts and relaxes during inhalation and exhalation respectively. During normal and quiet inhalation, the diaphragm and external intercostal muscles contract. The contraction of the diaphragm makes it flat to increase the volume of the thoracic cavity. This allows the lungs to expand and the pulmonary air pressure is reduced. The atmospheric air moves into the lungs.