How does movement of the diaphragm affect thoracic pressure?

The movement of the diaphragm plays a crucial role in the mechanics of breathing, particularly in relation to thoracic pressure. When the diaphragm contracts and moves downward, it expands the thoracic cavity, which in turn decreases the pressure inside the thoracic cavity. This drop in pressure creates a negative pressure environment that allows air to flow into the lungs as the body attempts to equalize the pressure difference between the atmosphere and the internal thoracic space, facilitating inhalation.

During exhalation, the diaphragm relaxes, and it moves back up into a dome shape, which reduces the volume of the thoracic cavity and, consequently, increases the pressure, helping to push air out of the lungs. However, the correct answer focuses on the effect during inhalation, where the contraction of the diaphragm is what leads to a decrease in thoracic pressure. Thus, understanding the diaphragm's downward movement and its effect on thoracic volume and pressure is essential to grasping how breathing mechanics function.