Question

During inspiration, the diaphragm__________________ and the expansion of the thoracic cavity is in the ___________________ direction

• A. contracts, dorso-ventral
• B. contracts, longitudinal
• C. relaxes, dorso-ventral
• D. relaxes, longitudinal

Answer 1

The correct option is B contracts, longitudinal

The diaphragm is a dome-shaped muscular structure that separates the thoracic cavity and the abdominal cavity. Inspiration is a process in which the air is drawn into the lungs. During inspiration, the diaphragm contracts because of which it gets pulled down and the thoracic cavity expands in the longitudinal direction. Within the lungs, due to the increase in volume, the pressure decreases and air enters into the lungs.

During inspiration, the external intercostal muscles also contract due to which the chest expands upwards and outwards and the volume of the thoracic cavity increases in the dorsoventral direction.
During expiration, the external intercostal muscles relax due to which the chest moves downwards and inwards and the volume of the thoracic cavity decreases in the dorsoventral direction.
Also, while breathing out the diaphragm relaxes and the volume of the thoracic cavity decreases in the longitudinal direction.