What is the primary function of the diaphragm in respiration?

The primary function of the diaphragm in respiration is to contract and expand the thoracic cavity. When the diaphragm contracts, it moves downward, which increases the volume of the thoracic cavity. This decrease in pressure within the cavity allows air to be drawn into the lungs. Conversely, when the diaphragm relaxes, it moves upward, decreasing the volume and increasing the pressure in the thoracic cavity, which helps push air out of the lungs. This process is essential for inhalation and exhalation, making the diaphragm a crucial muscle involved in the mechanics of breathing.

The other options involve functions that are not related to the diaphragm's role in respiration. Filtering toxins from the blood is primarily the function of the kidneys and liver. Producing insulin and regulating blood glucose pertains to the pancreas, not the diaphragm. Providing voluntary control over breathing mainly involves higher brain functions and does not specifically relate to the diaphragm’s primary mechanical role in respiration.