The colon (large intestine) is the distal part of the cradle tract, prolonging from the cecum to the anal canal. That receives spend food indigenous the small intestine, indigenous which it absorbs water and electrolytes to form faeces.

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Anatomically, the colon have the right to be split into four parts – ascending, transverse, descending and sigmoid. These sections type an arch, i m sorry encircles the little intestine.

In this article, we shall look at the anatomy that the colon – the anatomical structure and also relations, neurovascular supply, and also clinical correlations.


Anatomical Position

The colon averages 150cm in length, and also can be split into four parts (proximal to distal): ascending, transverse, descending and also sigmoid.

Ascending Colon

The colon begins together the ascending colon, a retroperitoneal structure which ascends superiorly native the cecum.

When the meets the ideal lobe that the liver, it turns 90 degrees to move horizontally. This rotate is recognized as the right colic flexure (or hepatic flexure), and marks the start of the transverse colon.

Transverse Colon

The transverse colon extends native the best colic flexure to the spleen, whereby it turns an additional 90 levels to point inferiorly. This turn is known as the left colic flexure (or splenic flexure). Here, the colon is attached to the diaphragm through the phrenicocolic ligament.

The transverse colon is the the very least fixed component of the colon, and also is change in place (it can dip right into the pelvis in tall, thin individuals). Uneven the ascending and also descending colon, the transverse colon is intraperitoneal and is fastened by the transverse mesocolon.

Descending Colon

After the left colic flexure, the colon move inferiorly towards the pelvis – and is dubbed the descending colon. That is retroperitoneal in the bulk of individuals, but is situated anteriorly come the left kidney, passing end its lateral border.

When the colon starts to rotate medially, it becomes the sigmoid colon.

Sigmoid Colon

The 40cm long sigmoid colon is located in the left lower quadrant of the abdomen, prolonging from the left iliac fossa come the level that the S3 vertebra. This journey offers the sigmoid colon its characteristics “S” shape.

The sigmoid colon is attached come the posterior pelvic wall surface by a mesentery – the sigmoid mesocolon. The long length of the mesentery permits this part of the colon to be particularly mobile.


Blausen gallery 2014 , via Wikimedia Commons
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Fig 1 – overview of the 4 main parts of the colon.


Paracolic Gutters

The paracolic gutters are two spaces between the ascending/descending colon and the posterolateral abdominal wall.

These structures room clinically important, together they enable material that has been exit from inflamed or infected abdominal organs to accumulate somewhere else in the abdomen.


Anatomical Structure

The huge intestine has a variety of characteristic features, which allows it to be identified from the small intestine:

Attached come the surface ar of the large intestine space omental appendices – small pouches of peritoneum, filled with fat.Running longitudinally follow me the surface ar of the huge bowel are three strips that muscle, well-known as the teniae coli. Lock are dubbed the mesocolic, complimentary and omental coli.The teniae coli contract to shorten the wall of the bowel, producing sacculations well-known as haustra.The large intestine has a much wider diameter compared to the little intestine.

These attributes cease at the rectosigmoid junction, whereby the smooth muscle of the teniae coli expand to form a complete layer within the rectum.


By OpenStax college , via Wikimedia Commons
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Fig 2 – The macroscopic features of the large intestine.


Neurovascular Supply

The neurovascular it is provided to the colon is carefully linked come its embryological origin:

Ascending colon and proximal 2/3 the the transverse colon – derived native the midgut.Distal 1/3 the the transverse colon, to decrease colon and also sigmoid colon – derived indigenous the hindgut.

Arterial Supply

As a basic rule, midgut-derived structures are provided by the remarkable mesenteric artery, and hindgut-derived frameworks by the worse mesenteric artery.

The ascending colon receives arterial supply from two branches of the superior mesenteric artery; the ileocolic and also right colic arteries. The ileocolic artery provides rise to colic, anterior cecal and also posterior cecal branches – all of which supply the ascending colon.

The transverse colon is acquired from both the midgut and also hindgut, and so the is provided by branches of the exceptional mesenteric artery and also inferior mesenteric artery:

Right colic artery (from the superior mesenteric artery)Middle colic artery (from the remarkable mesenteric artery)Left colic artery (from the inferior mesenteric artery)

The to decrease colon is offered by a single branch that the worse mesenteric artery; the left colic artery. The sigmoid colon receives arterial it is provided via the sigmoid arteries (branches of the inferior mesenteric artery).


Marginal Artery the Drummond

The marginal artery (of Drummond) is a clinically important vessel that provides collateral supply come the colon – thereby keeping arterial supply in the case of occlusion or stenosis of one of the major vessels.

As the terminal ship of the exceptional mesenteric and inferior mesenteric artery technique the colon, they break-up into plenty of branches, i m sorry anastomose v each other. These anastomoses kind a constant arterial channel i beg your pardon extends the length of the colon – the marginal artery. Long, right arterial branches (called vasa recta) arise native the marginal artery to supply the colon.


Venous Drainage

The venous drainage that the colon is comparable to the arterial supply:

Ascending colon – ileocolic and right colic veins, i beg your pardon empty right into the superior mesenteric vein.Transverse colon – middle colic vein, i m sorry empties into the premium mesenteric vein.Descending colon – left colic vein, which drains right into the inferior mesenteric vein.Sigmoid colon – drained by the sigmoid veins right into the inferior mesenteric vein.

The remarkable mesenteric and inferior mesenteric veins eventually empty right into the hepatic portal vein. This permits toxins took in from the colon to be processed by the liver because that detoxification.


by TeachMeSeries Ltd (2021)
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Fig 3 – The major arteries and also veins offering the colon.


Innervation

The innervation to the colon is dependency on embryological origin:

Midgut-derived structures (ascending colon and proximal 2/3 the the transverse colon) receive their sympathetic, parasympathetic and sensory it is provided via nerves indigenous the exceptional mesenteric plexus.

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Hindgut-derived structures (distal 1/3 that the transverse colon, diminish colon and also sigmoid colon) receive their sympathetic, parasympathetic and also sensory it is provided via nerves from the inferior mesenteric plexus:Parasympathetic innervation via the pelvic splanchnic nervesSympathetic innervation via the lumbar splanchnic nerves.