Transverse colon
Colon transversum
The transverse colon is the longest and most mobile part of the large intestine. It hangs on the transverse mesocolon between the hepatic and splenic flexures.
Overview
The transverse colon is about 45–50 cm long. It runs from the right colic (hepatic) flexure to the left colic (splenic) flexure in a downward-sagging U shape, which may reach the pelvis in tall people when standing. It is intraperitoneal, suspended by the transverse mesocolon, whose root runs across the head and anterior border of the pancreas. The greater omentum is fused to its anterior surface (the gastrocolic ligament).
The splenic flexure lies higher, at about the 10th–11th rib, and is sharper and more posterior than the hepatic flexure. It is held to the diaphragm by the phrenicocolic ligament. The transverse colon marks an embryological and neurovascular boundary. Its proximal two-thirds is midgut (SMA, vagus) and its distal third is hindgut (IMA, pelvic splanchnic nerves).
- Location
Crosses the abdomen in the umbilical region and upper abdomen, below the stomach and liver, from the right to the left upper quadrant.
Anatomy
- Innervation
Proximal two-thirds: vagus nerve and superior mesenteric plexus. Distal third: pelvic splanchnic nerves (S2–S4) and inferior mesenteric plexus.
- Arterial supply
Middle colic artery (SMA) for most of its length, the right colic artery near the hepatic flexure, and the left colic artery (IMA) for the distal third. The marginal artery links them. The watershed lies at the splenic flexure.
- Venous drainage
Middle colic vein → superior mesenteric vein. Distal third → inferior mesenteric vein.
- Lymphatic drainage
Middle colic nodes → superior mesenteric nodes; distal third → inferior mesenteric nodes.
- Relations
Superior: liver, gallbladder, greater curvature of the stomach and spleen. Posterior: 2nd part of the duodenum, head of the pancreas and loops of jejunum and ileum. Anterior: greater omentum and the anterior abdominal wall.
- Development
It is the junction of midgut and hindgut; the change in blood supply and innervation occurs about two-thirds of the way along.
Function
- Absorbs water and electrolytes.
- Transports contents by mass movements and stores faeces temporarily.
Clinical significance
Toxic megacolon
A life-threatening complication of severe ulcerative colitis (or infective colitis such as C. difficile). Typically the transverse colon dilates to more than 6 cm with systemic toxicity, and there is a high risk of perforation.
Splenic flexure ischaemia
The watershed between the SMA and IMA territories (Griffiths point) is vulnerable when flow is low. It is a classic site of ischaemic colitis.
Test yourself
Which organ is intraperitoneal (NOT retroperitoneal)?
- Descending colon
- Head of the pancreas
- Transverse colon
- Second part of the duodenum
Answer: Transverse colon
The transverse colon hangs on the transverse mesocolon and is intraperitoneal. The other three are secondarily retroperitoneal (SAD PUCKER).
The superior mesenteric artery supplies the gut from:
- The lower oesophagus to the major duodenal papilla
- The major duodenal papilla to the proximal two-thirds of the transverse colon
- The distal third of the transverse colon to the pectinate line
- The jejunum to the sigmoid colon
Answer: The major duodenal papilla to the proximal two-thirds of the transverse colon
The SMA (L1) supplies the midgut, from just distal to the major papilla to the proximal two-thirds of the transverse colon. The coeliac trunk supplies the foregut, and the IMA supplies the hindgut down to the pectinate line.
Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.