Small intestine is the longest part of the digestive tract, about 5 to 6 meters, the inner surface has many circular folds. The beginning of the small intestine is equivalent to the length of twelve fingers side by side, so it is called the duodenum (combined with wall charts see explanation), the small intestine is the main organ of digestion and absorption.

The large intestine is thicker than the small intestine, the length of about 1.5 meters, can be divided into the cecum, colon and rectum three parts.

In the beginning of the large intestine (connected with the small intestine), there is a downward protruding blind sac, known as the cecum, the blind end of which there is a finger-like protrusion, that is, the appendix. Both the cecum and the appendix are degenerate organs in the body. The large intestine has some absorptive function.