diaphragm muscle

The diaphragm muscle - The dome-shaped sheet of muscle that separates the chest from the abdomen. The diaphragm is attached to the spine, ribs, and sternum (breastbone). It has openings for the oesophagus and major nerves and blood vessels.

The diaphragm plays an important role in breathing. During inhalation, its muscle fibres contract, causing it to move downwards and drawing air into the lungs. During exhalation, the diaphragm muscle relaxes and it moves upwards, causing air to leave the lungs. (See also breathing.)