caecum

The caecum, also spelled cecum, is the blind-ended first portion of the large intestine. In humans it lies in the right lower abdomen, typically within the right iliac fossa, and is intraperitoneal. The ileum opens into the caecum through the ileocecal valve, and the vermiform appendix arises from the caecum near its posteroinferior wall.

From the caecum the colon begins with a short ascending segment. The ileocecal valve helps regulate the passage of contents from the ileum into the caecum and prevents reflux of colonic material into the small intestine.

Functionally, the caecum participates in absorbing water and electrolytes and hosts a community of gut bacteria. In herbivorous species it plays a more prominent role in fermentation of plant material; in humans its fermentative activity is comparatively limited.

Blood supply is via the ileocolic artery, a branch of the superior mesenteric artery, with venous drainage to the portal system through the ileocolic veins. Innervation comes from the superior mesenteric plexus, and lymphatic drainage goes to the ileocolic lymph nodes.

Clinically, the caecum is a site of appendiceal inflammation and can be involved in caecal diverticula, caecal volvulus, Crohn disease, and mucosal or mural tumors. Its position and mobility can vary with developmental factors such as intestinal rotation and fixation anomalies. Developmentally, the caecum arises from the midgut during embryogenesis and undergoes final positioning during intestinal rotation.