Air moves down the trachea, a long straight tube in the chest. The diaphragm pulls air in and pushes it out. Behind the nasal cavity, air next passes through the pharynx, a long tube that is shared with the digestive system. Both food and air pass through the pharynx. A flap of connective tissue called the epiglottis closes over the trachea when food is swallowed to prevent choking or inhaling food. In humans, the pharynx is important in vocalization.
