Mechanical and Chemical Digestion

The human digestive system consists of the alimentary canal and the associated glands that pour secretions into this canal. The alimentary canal consists of the entire path of food through the body: the oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and rectum. Many glands line this canal, such as the gastric glands in the wall of the stomach and intestinal glands in the small intestine. Other glands, like the pancreas and liver, are outside the canal proper, and pour their secretions into the canal via ducts.

Mechanical Digestion - Food is crushed and liquefied by the teeth, tongue, and peristaltic contractions (waves of involuntary muscle contraction) of the stomach and small intestine. This creates a greater surface area for the digestive enzymes to work upon.

Chemical Digestion - Many glandular structures, dispersed throughout the body, are involved in breaking food into simple molecules that can be absorbed. In the mouth, the salivary glands produce saliva, which both lubricates food and begins the process of starch digestion. Saliva contains salivary amylase (ptyalin), an enzyme that digests starch to maltose (a disaccharide). As food leaves the mouth, the esophagus conducts it to the stomach via the cardiac sphincter by means of peristaltic waves of smooth muscle contraction.

This animation (Audio - Important) describes the digestive system.

PREVIOUS