What is the primary muscle used for breathing in the human body?

The diaphragm is the primary muscle used for breathing in the human body.

This dome-shaped sheet of skeletal muscle separates the thoracic cavity from the abdominal cavity. When the diaphragm contracts, it moves downward and flattens. That increases the volume of the chest cavity and lowers pressure inside the lungs, drawing air inward. When it relaxes during quiet breathing, it rises again as the lungs and chest wall recoil.

The muscles between the ribs, called intercostal muscles, also assist breathing by moving the rib cage. During vigorous exercise or respiratory difficulty, additional muscles in the neck and chest can contribute. The diaphragm contains openings for structures including the oesophagus, aorta, and inferior vena cava. It also plays roles in coughing, sneezing, vomiting, and helping generate pressure for movements such as lifting.