The colon and rectum are parts of the digestive system. They form a long, muscular tube called the large intestine (also called the large bowel). The colon is the first 4 to 5 feet of the large intestine, and the rectum is the last several inches.

Partly digested food enters the colon from the small intestine. The colon removes water and nutrients from the food and turns the rest into waste (stool). The waste passes from the colon into the rectum and then out of the body through the anus.

This picture shows the colon and rectum.

Source: National Cancer Institute

Colorectal Cancer:
The Colon & Rectum- Anatomy
Understanding Cancer
Risk Factors
Screening
Symptoms
Staging
Treatment