Transverse colon

At a glance

English

Transverse colon

Latin (TA2)

Colon transversum

System

Digestive

Region

Abdomen

Side

Single, on the midline

About the transverse colon

The transverse colon crosses the abdomen from the right colic (hepatic) flexure under the liver to the left colic (splenic) flexure beside the spleen. It is about 45 cm long, the longest part of the colon. Because it is slung on a long mesentery between two fixed ends, it does not run straight but sags downwards in a curve, sometimes reaching the umbilicus or even into the pelvis when a person stands. The left end lies higher and further back than the right.

Unlike the ascending and descending colon, it is intraperitoneal. The transverse mesocolon attaches it to the posterior abdominal wall along a root crossing the head and body of the pancreas, and the greater omentum descends in front of it and blends with its upper surface along the omental taenia. Above it are the liver, gallbladder, stomach and spleen; behind it, the duodenum and pancreas; below it, the coils of small intestine. The transverse colon and its mesocolon split the peritoneal cavity into an upper (supracolic) and a lower (infracolic) compartment.

It shows the usual colonic features of taeniae, haustra and omental appendices. Its mucosa continues to absorb water and salts, and mass movements, strong waves of contraction often triggered by eating, sweep contents along it towards the descending colon. Bacteria in its lumen ferment remaining carbohydrate.

The transverse colon is where the territory of the midgut meets that of the hindgut: roughly the right two-thirds depend on the middle colic artery (a superior mesenteric branch) and the left third by inferior mesenteric vessels. The splenic flexure is therefore a watershed area, prone to poor blood flow (ischaemic colitis) when pressure falls. Its mobility means it may twist, and its position just below the stomach makes it easy to reach in colonoscopy and abdominal surgery.

Function and supply

Function

Absorbs water and salts, stores and mixes contents, and passes them to the descending colon by mass movements.

Nerve supply

Right two-thirds: vagal fibres and the superior mesenteric plexus. Left third: pelvic splanchnic nerves and the inferior mesenteric plexus.

Blood supply

Mainly the middle colic artery from the superior mesenteric artery, with right colic and left colic contributions at each end through the marginal artery.