During which phase of respiration does the diaphragm contract and move down?

The phase of respiration in which the diaphragm contracts and moves downward is inspiration. During this process, the diaphragm, a dome-shaped muscle located below the lungs, contracts and flattens. This contraction increases the volume of the thoracic cavity, causing a decrease in the internal pressure relative to the atmospheric pressure outside the body. As a result, air flows into the lungs. The movement of the diaphragm is essential for the inhalation of air, allowing oxygen to enter the respiratory system for gas exchange.

In the context of respiration, expiration refers to the release of air from the lungs, during which the diaphragm relaxes and moves back to its original position. External respiration involves the exchange of gases between the atmosphere and the blood in the lungs. Internal respiration, on the other hand, refers to the exchange of gases between the bloodstream and the body tissues. While all these processes contribute to respiration, it is specifically during inspiration that the diaphragm's contraction and downward movement occur.