Diaphragm
The diaphragm is a slate of skeletal muscle that lies along the bottom of the ribcage. It acts as a barrier between the thoracic cavity and the abdominal cavity. It also plays a major role in the respiratory system. The diaphragm is what allows the lungs to expand and contract. When a person breathes in, the diaphragm flattens out and makes room in the lungs for air. When the body is ready to exhale, the diaphragm rises and expands, decreasing the volume in the lungs, forcing the air back up the trachea and out the nose/mouth.