tykktarmen

Tykktarmen, commonly referred to in English as the colon, is the final section of the digestive tract in humans. It extends from the ileocecal valve to the rectum and averages about 1.5 meters in length. Its primary functions are absorption and stool formation.

Anatomy: The tykktarmen comprises the caecum, the colon (ascending, transverse, descending, and sigmoid segments), and the rectum. The colon features haustrations and taeniae coli and ends at the rectosigmoid junction. The ileocecal valve regulates flow from the ileum into the colon.

Function: It absorbs water and electrolytes, concentrates waste, and stores feces until defecation. It also hosts a diverse microbiota that ferments certain undigested carbohydrates and produces vitamins such as vitamin K and short-chain fatty acids beneficial to colonic health.

Blood supply and innervation: The proximal colon is supplied by the superior mesenteric artery, while the distal colon and rectum receive blood from the inferior mesenteric artery. Venous drainage returns to the portal system. Parasympathetic input arises mainly from pelvic splanchnic nerves; sympathetic input from mesenteric plexuses.

Clinical relevance: Common conditions include colorectal cancer, diverticular disease, inflammatory bowel disease, polyps, constipation, and diarrhea. Screening colonoscopy from middle age reduces mortality. Symptoms may include rectal bleeding, abdominal pain, changes in bowel habit, or a sense of incomplete evacuation.

Notes: In Norwegian and Danish, tykktarmen refers to the same structure; in English texts the term colon or large intestine is used.