What are some examples of mechanical digestion?

Mastication Swallowing Peristalsis Absorption Defecation

Mechanical digestion is the physical act of breaking down the food by non-chemical means.

Mechanical digestion begins in the mouth by the physical act of mastication (chewing). The specialized teeth break down the food as it is cut by the incisors, torn by the cuspids and ground by the molars.

The food is manipulated in the mouth by the tongue, and cheeks to mix and moisten the food forming a bolus or ball which is pushed to the back of the tongue.

Swallowing occurs when the tongue slides back and locks the epiglottis over the larynx which allows the bolus to be pushed into the esophagus.

The bolus is then pushed by wave-like muscular contractions called peristalsis that moves the food to the stomach.

In the stomach the food is churned by peristalsis in order to mix with the gastric juices and pushed to the pyloric sphincter at the base of the stomach. The food which is now a paste called chyme is pushed through the pylorus into the duodenum the first loop of the small intestine.

The chyme is pushed through the small intestine by peristalsis allowing the absorption of food nutrients by the villi lining the intestinal walls.

This peristalsis and absorption continues through both the small and large intestine. Osmosis pulls most of the water out in the large intestine. The remaining waste called feces is gathered in the sigmoid colon until a mass movement called defecation releases the waste through the rectum and anus.