The Intestines are a long, continuous tube running from the stomach to the anus. Most absorption of nutrients and water happen in the intestines. The intestines include the small intestine, large intestine, and rectum.
The small intestine (small bowel) is about 20 feet long and about an inch in diameter. Its job is to absorb most of the nutrients from what we eat and drink. Velvety tissue lines the small intestine, which is divided into the duodenum, jejunum, and ileum.
The large intestine (colon or large bowel) is about 5 feet long and about 3 inches in diameter. The colon absorbs water from wastes, creating stool. As stool enters the rectum, nerves there create the urge to defecate.

What happens when the intestines are not working properly?

Have you ever had a 'tummy ache'?
Maybe you have felt like you really wanted to do a poo but just couldn't? You could have been constipated. This means that the waste is too hard or dry to be able to slide out when you go to the toilet.
Maybe you had really runny poo and needed to hang out near the loo just in case you had an accident? This is called diarrhoea (di-a-ree-a).
Sometimes, when children and adults get worried about something, they feel a pain in their tummy, and sometimes even have runny poo. This does not cause any harm, but it can be quite uncomfortable.
Usually things get better but sometimes problems can be more serious.
Irritable bowel syndrome is caused by the nerves controlling the muscles of the intestines. It can cause tummy ache, diarrhoea or constipation, and a feeling like you're full of air (bloated).
Inflammatory bowel syndrome has similar symptoms but it is more serious and is harder to treat. One type, called Crohn's disease causes ulcers, bleeding and irritation in the bowel.
Cancer of the bowel is one of the more common types of cancer that people get.