Diaphragm

Diaphragm forms a muscular sheet anchored to the lower ribs, sternum, and lumbar vertebrae. At rest it curves upward into the thoracic cavity, but when the muscle fibers contract, the dome flattens, enlarging the chest space. This drop in pressure draws air into the lungs like a bellows.

During exhalation, the diaphragm relaxes and springs back into its dome shape, pushing air out as the lungs recoil. Although breathing continues automatically under brainstem control, we can also voluntarily hold our breath or deepen inhalations, which singers, divers, and athletes practice to expand lung capacity.

The diaphragm includes three key openings: the caval hiatus for the inferior vena cava, the esophageal hiatus for the esophagus and vagus nerves, and the aortic hiatus for the aorta. These passages ensure blood flow and food transit continue unhindered even while the muscle moves constantly.

Hiccups occur when the diaphragm spasms suddenly, closing the vocal cords with a sharp sound. More serious problems include diaphragmatic paralysis from nerve injury, or hiatal hernias when part of the stomach slips through the esophageal hiatus. Physicians assess diaphragm function using imaging, pulmonary tests, and nerve studies, and may recommend breathing exercises or surgical repair.

Keeping the diaphragm strong involves regular aerobic activity, good posture, and mindful breathing that engages the abdominal wall. Practicing diaphragmatic breathing can lower stress, improve singing or wind-instrument performance, and aid people with asthma or COPD by encouraging full lung expansion.