Colonic mucosa

The colonic mucosa is the inner lining of the colon, a long, tube-shaped organ that forms part of the digestive tract. The colon starts at the end of the small intestine (ileum) and extends to the anal canal. The mucosa helps absorb water and nutrients and also protects the colon by producing mucus.

What are the layers of the colonic mucosa?

The colonic mucosa consists of three main layers:

• Epithelium: This is the topmost layer, composed of specialized cells that form glands. These glands help absorb water and produce mucus, which keeps the colon moist and protected.
• Lamina propria: A thin layer of connective tissue beneath the epithelial layer that supports and nourishes the epithelium. It contains tiny blood vessels and immune cells.
• Muscularis mucosa: A thin layer of muscle beneath the lamina propria that helps move and gently contract the mucosa.

What medical conditions involve the colonic mucosa?

Several medical conditions affect or originate in the colonic mucosa:

• Colonic polyps: Common growths such as tubular adenomas, tubulovillous adenomas, villous adenomas, and sessile serrated lesions develop from cells within the mucosa.
• Colon cancer: Adenocarcinoma, the most common type of colon cancer, starts in cells of the colonic mucosa.
• Inflammatory bowel diseases: Conditions like Crohn’s disease and ulcerative colitis involve chronic inflammation of the colonic mucosa.
• Microscopic colitis: An inflammatory condition affecting the mucosal layer, causing symptoms such as diarrhea and abdominal discomfort.

How do doctors examine the colonic mucosa?

Doctors often examine the colonic mucosa using a procedure called colonoscopy. During a colonoscopy, a small flexible camera is inserted into the colon to visually inspect the mucosa. A small tissue sample, known as a biopsy, can also be taken during this procedure to examine the mucosa under a microscope. This helps diagnose various conditions, including polyps, cancer, and inflammatory diseases.