Thoracic diaphragm

In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm, is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity (heart, lungs & ribs) from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases and air is drawn into the lungs.