The fleshy membrane located transversely between the thoracic cavity and the abdominal cavity is called diaphragm. It is made up of voluntary muscles. During inhalation the diaphragm contracts, descends and flattens. As a result, the volume of the lungs increases and air enters the lungs. During exhalation it expands, rises upwards and bends like a bow. As a result, the volume of the lungs decreases and air escapes from the lungs.