Name the primary muscle responsible for inhalation.

The primary muscle responsible for inhalation is the diaphragm. This dome-shaped muscle is located at the base of the thoracic cavity and plays a crucial role in the respiratory process. During inhalation, the diaphragm contracts, which causes it to flatten and descend. This action increases the volume of the thoracic cavity, leading to a decrease in internal pressure relative to atmospheric pressure. As a result, air is drawn into the lungs.

While the intercostal muscles also assist during inhalation by helping to elevate the rib cage and expand the chest cavity, the diaphragm is the main muscle that initiates the process. The abdominal muscles and rectus abdominis are primarily involved in exhalation and do not contribute significantly to the process of inhalation. Thus, the diaphragm stands out as the key player in enabling effective breathing.