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Digestive health centre

Picture of the intestines

Did you know the small intestine, or small bowel, is around six metres (20 feet) long and around 2.5cm (an inch) in diameter? Learn more about the intestines, and their role in absorbing the nutrients from food and drink.

The intestines are a long, continuous tube running from the stomach to the anus. Food is propelled along by waves of muscular contraction known as peristalsis. Most absorption of nutrients and water happen in the intestines. The intestines include the small intestine, large intestine and rectum.

Illustration of Human Intestines

Velvety tissue lines the small intestine, which is divided into the duodenum, jejunum and ileum.

The large intestine (colon or large bowel) is about 1.5m (5 feet) long and about 7.6cm (3 inches) in diameter. The colon absorbs water from wastes, creating stool. As stool enters the rectum, nerves there create the urge to defecate.

Intestine conditions

Enteritis: Inflammation of the small intestine. Infections (from viruses, bacteria or parasites) are the common cause, often due to food poisoning.

Small intestine cancer: Rarely, cancer may affect the small intestine. There are multiple types of small intestine cancer.

Coeliac disease: An adverse reaction to gluten (a protein from wheat and some other grains found in most breads) causes the small intestine not to absorb nutrients properly. Abdominal pain and weight loss are usual symptoms.

Carcinoid tumour: A benign or malignant growth in the small intestine. Diarrhoea and skin flushing are the most common symptoms.

Intestinal obstruction: A section of either the small or large bowel can become blocked or twisted or just stop working. Abdominal distension, pain, constipation and vomiting are symptoms.

Colitis: Inflammation of the colon. Inflammatory bowel disease or infections are the most common causes.

Diverticulosis: Small weak areas in the colon's muscular wall allow the colon's lining to protrude through, forming tiny pouches called diverticuli. Diverticuli usually cause no problems, but can bleed or become inflamed.

Diverticulitis: When diverticuli become inflamed or infected, diverticulitis results. Abdominal pain and constipation are common symptoms.

Colon bleeding (haemorrhage): Multiple potential colon problems can cause bleeding. Evidence of  bleeding may or may not be visible in the stool.

Inflammatory bowel disease: A name for either Crohn's disease or ulcerative colitis. Both conditions can cause bowel inflammation (colitis).

Crohn's disease: An inflammatory condition that can affect both the small, and large intestines. Abdominal pain and diarrhoea (which may be bloody) are symptoms.

Ulcerative colitis: An inflammatory condition that affects the bowel and rectum. Like Crohn's disease, bloody diarrhoea is a common symptom of ulcerative colitis.

Diarrhoea: Stools that are frequent, loose or watery are commonly called diarrhoea. Most diarrhoea is due to self-limited, mild infections of the bowel or small intestine.

Salmonellosis: Salmonella bacteria can contaminate food and infect the intestine. Salmonella causes diarrhoea and stomach cramps, which usually resolve without treatment.

WebMD Medical Reference

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