What is the primary function of the diaphragm in mammals?

The diaphragm's primary function is to act as a sheet of muscle that forms the bottom wall of the thoracic cavity. This muscle plays a crucial role in the process of respiration. When the diaphragm contracts, it moves downward, increasing the volume of the thoracic cavity. This decrease in pressure allows air to flow into the lungs, facilitating inhalation. During exhalation, the diaphragm relaxes and moves back upward, helping to expel air from the lungs.

This explanation underscores its fundamental role in breathing, distinguishing it from other functions such as aiding blood circulation, providing protection to the lungs, or being particularly involved in involuntary reflexes. Understanding the diaphragm's specific function within the thoracic cavity is key to grasping how respiration works in mammals.