The diaphragm plays a vital role in respiration as the main muscle responsible for the process of inhalation. When the diaphragm contracts, it moves downward, expanding the thoracic cavity and reducing internal pressure. This action draws air into the lungs. During exhalation, the diaphragm relaxes and moves upward, pushing air out. This rhythmic contraction and relaxation are essential for proper breathing and gas exchange in the lungs.