Digestion and Absorption

Digestion is the process by which large, insoluble food molecules are broken down into small, soluble molecules that can be absorbed into the bloodstream and used by cells. In humans this occurs along the alimentary canal, a continuous muscular tube running from the mouth to the anus, assisted by accessory organs such as the salivary glands, pancreas, liver, and gallbladder.

The Alimentary Canal

Food is moved along the gut by peristalsis, rhythmic waves of contraction and relaxation of the circular and longitudinal muscle layers in the gut wall. Mechanical digestion begins in the mouth, where teeth grind food into smaller pieces, increasing the surface area available to enzymes. The stomach churns food and mixes it with acidic gastric juice, producing a semi-liquid mixture called chyme. Th