bagasfen.blogg.se - Sigmoidal flexture

These sections form an arch, which encircles the small intestine. It receives digested food from the small intestine, from which it absorbs water and electrolytes to form faeces.Īnatomically, the colon can be divided into four parts - ascending, transverse, descending and sigmoid. The colon (large intestine) is the distal part of the gastrointestinal tract, extending from the cecum to the anal canal. This allows toxins absorbed from the colon to be processed by the liver for detoxification. The superior mesenteric and inferior mesenteric veins ultimately empty into the hepatic portal vein.

Sigmoid colon – drained by the sigmoid veins into the inferior mesenteric vein.

Descending colon – left colic vein, which drains into the inferior mesenteric vein.

Transverse colon – middle colic vein, which empties into the superior mesenteric vein.

Ascending colon – ileocolic and right colic veins, which empty into the superior mesenteric vein.

The venous drainage of the colon is similar to the arterial supply: Long, straight arterial branches (called vasa recta) arise from the marginal artery to supply the colon. The marginal artery (of Drummond) is a clinically important vessel that provides collateral supply to the colon – thereby maintaining arterial supply in the case of occlusion or stenosis of one of the major vessels.Īs the terminal vessels of the superior mesenteric and inferior mesenteric artery approach the colon, they split into many branches, which anastomose with each other. These anastomoses form a continuous arterial channel which extends the length of the colon – the marginal artery. The descending colon is supplied by a single branch of the inferior mesenteric artery the left colic artery. The sigmoid colon receives arterial supply via the sigmoid arteries (branches of the inferior mesenteric artery).

Left colic artery (from the inferior mesenteric artery).

Middle colic artery (from the superior mesenteric artery).

Right colic artery (from the superior mesenteric artery).

The transverse colon is derived from both the midgut and hindgut, and so it is supplied by branches of the superior mesenteric artery and inferior mesenteric artery: The ileocolic artery gives rise to colic, anterior cecal and posterior cecal branches – all of which supply the ascending colon. The ascending colon receives arterial supply from two branches of the superior mesenteric artery the ileocolic and right colic arteries.

Distal 1/3 of the transverse colon, descending colon and sigmoid colon – derived from the hindgut.Īs a general rule, midgut-derived structures are supplied by the superior mesenteric artery, and hindgut-derived structures by the inferior mesenteric artery.

Ascending colon and proximal 2/3 of the transverse colon – derived from the midgut.

The neurovascular supply to the colon is closely linked to its embryological origin: The long length of the mesentery permits this part of the colon to be particularly mobile. The sigmoid colon is attached to the posterior pelvic wall by a mesentery – the sigmoid mesocolon. This journey gives the sigmoid colon its characteristic “S” shape. The 40cm long sigmoid colon is located in the left lower quadrant of the abdomen, extending from the left iliac fossa to the level of the S3 vertebra. When the colon begins to turn medially, it becomes the sigmoid colon. It is retroperitoneal in the majority of individuals, but is located anteriorly to the left kidney, passing over its lateral border. Descending ColonĪfter the left colic flexure, the colon moves inferiorly towards the pelvis – and is called the descending colon. Unlike the ascending and descending colon, the transverse colon is intraperitoneal and is enclosed by the transverse mesocolon.

The transverse colon is the least fixed part of the colon, and is variable in position (it can dip into the pelvis in tall, thin individuals). Here, the colon is attached to the diaphragm by the phrenicocolic ligament. This turn is known as the left colic flexure (or splenic flexure). The transverse colon extends from the right colic flexure to the spleen, where it turns another 90 degrees to point inferiorly. This turn is known as the right colic flexure (or hepatic flexure), and marks the start of the transverse colon. When it meets the right lobe of the liver, it turns 90 degrees to move horizontally. The colon begins as the ascending colon, a retroperitoneal structure which ascends superiorly from the cecum. The colon averages 150cm in length, and can be divided into four parts (proximal to distal): ascending, transverse, descending and sigmoid.