September 5, 2023
The colon or large intestine is an organ and a part of the gastrointestinal tract. It is a long hollow tube that starts at the small bowel and ends at the anal canal. The colon is divided into several sections, including the ascending (right) colon, transverse colon, descending (left) colon, and sigmoid colon. It ends at the rectum, which connects to the anal canal.
The inside of the colon is covered by specialized epithelial cells that connect together to form long straight glands. The epithelial cells in the colon produce mucin which helps move digested food along the length of the colon. The glands are found in a thin layer of tissue on the inside surface of the colon called the mucosa. Below the mucosa are layers of connective tissue and muscle. The outside surface of the colon is covered by fat and a thin layer of tissue called serosa.
The most common type of colon cancer is called adenocarcinoma. It starts from cells normally found on the inside surface of the colon.
The most common type of noncancerous tumour in the colon is called an adenoma. There are several types of adenomas in the colon including tubular, tubulovillous, and villous. While adenomas are considered noncancerous growths, they can turn into cancer over time.