Jämesool

Jämesool, or the large intestine, is the final section of the human digestive system, extending from the ileocecal valve to the anus. Its primary roles are absorbing water and electrolytes from indigestible food matter, forming and storing feces, and housing a large community of gut microbiota. The large intestine comprises the caecum, the colon (consisting of ascending, transverse, descending, and sigmoid segments), and the rectum.

In terms of anatomy and histology, the mucosa is lined by simple columnar epithelium with numerous goblet cells; unlike the small intestine, the colon has relatively flat mucosa without villi. The caecum connects to the ileum and marks the beginning of the colon; the rectum stores feces before defecation.

Functions include water and electrolyte absorption; mucus secretion to lubricate feces; formation and storage of fecal matter; microbial fermentation; and vitamin production (e.g., vitamin K and some B vitamins).

Circulation and innervation involve blood supply via the superior mesenteric artery to the cecum and much of the colon, and via the inferior mesenteric artery to the distal colon and rectum. Venous drainage follows arteries to the portal system. Parasympathetic innervation is via the vagus nerve to the proximal colon, while pelvic splanchnic nerves (S2-S4) innervate the distal colon and rectum; sympathetic fibers reach the region through mesenteric plexuses.

Clinical notes include conditions such as diverticulosis and diverticulitis, inflammatory bowel disease, and colorectal cancer. Screening methods, including colonoscopy, detect polyps or cancer, and dietary factors, fiber intake, and lifestyle influence bowel health.