Digestive system
Large Intestine (Colon)
The large intestine, or colon, absorbs water and salts from leftover food and forms and stores stool. It is also home to trillions of helpful gut bacteria.
What it is
The large intestine is a wide tube of about 1.5 metres framing the abdomen, including the colon and rectum.
Where it is
Framing the abdomen around the small intestine, ending at the rectum and anus.
What it does
Absorbs remaining water and salts, houses the gut microbiome, and forms, stores and passes stool.
How it works
Undigested material passes from the small intestine into the colon, where water is reabsorbed and the contents are gradually solidified into stool. Gut bacteria ferment some fibre, producing vitamins and beneficial substances, before waste is stored in the rectum until passed.
When things go wrong
Common conditions affecting the large intestine (colon)
- Irritable bowel syndrome (IBS)
- Diverticular disease
- Ulcerative colitis
- Bowel (colorectal) cancer
Education and reference only. This explains the anatomy in plain terms and is not a diagnosis. Sudden severe symptoms — such as severe chest pain, breathlessness or collapse — are an emergency; call 999.
Looking after it
Keeping your large intestine (colon) healthy
A high-fibre diet, staying active and hydrated, limiting processed and red meat, not smoking, and attending bowel cancer screening all protect the large bowel.
Did you know?
An interesting fact
The colon hosts trillions of bacteria — collectively the "gut microbiome" — which influence digestion, immunity and even mood.
Answers
Large Intestine (Colon): frequently asked questions
What does the large intestine do?
The large intestine (colon) absorbs water and salts from leftover food, houses gut bacteria, and forms and stores stool until it is passed.
Why does bowel screening matter?
Screening can find bowel cancer early, or find and remove growths (polyps) before they become cancer, which is why it is offered to eligible adults.
The digestive system
Related organs
Sources
Where this is drawn from
- NHS — Anatomy and body systems
- Gray's Anatomy for Students
- TeachMeAnatomy / TeachMePhysiology
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