Expansion
Caecum, ascending, transverse, descending and sigmoid colon, with hepatic and splenic flexures
Expansion
- Caecum - intraperitoneal, in the right iliac fossa
- Ascending colon - retroperitoneal
- Hepatic (right colic) flexure - below the liver
- Transverse colon - intraperitoneal, on the transverse mesocolon; the most mobile part
- Splenic (left colic) flexure - higher, more acute, anchored by the phrenicocolic ligament
- Descending colon - retroperitoneal
- Sigmoid colon - intraperitoneal, on the sigmoid mesocolon
The alternating fixed and mobile segments explain much of colonic pathology. The mobile sigmoid on a long narrow mesentery can twist, causing volvulus. The fixed retroperitoneal segments must be mobilised along the avascular embryological fusion plane to be resected.
The high, acute splenic flexure is also the hardest point of a colonoscopy and a watershed for blood supply.