Food enters the human digestive system through the mouth before then moving through the pharynx, esophagus, stomach, intestines, rectum and anus. In the mouth, food is chewed and broken down into small pieces suitable for digestion. The mouth produces more saliva to break down food into a form that the body can use and absorb. Next, food slides down the pharynx, which is also called the throat. Food is further swallowed in the pharynx as a reflex.
Food passes through the esophagus, which extends from the pharynx and behind the trachea, on its way to the stomach. Food is pushed through this muscular tube and into the stomach through a series of involuntary muscle contractions called peristalses. Near the opening to the stomach, the lower esophageal sphincter opens to allow food to pass into the stomach and closes to keep the food from going back into the esophagus. Stomach glands secrete enzymes and acid that turn the food into a liquefied substance called chyme. Glands also secrete mucous, which protects the stomach from ulcers. After a while, the food is reduced to chyme or sometimes a pasty, solid substance. This substance enters the small and large intestines. The small intestine further breaks down the food by producing digestive enzymes. The large intestine removes water and electrolytes from the food. Finally, the waste product is stored in the rectum and excreted through the anus.
