The mesentery is a twin fold of peritoneal tissue that suspends the little intestine and huge intestine native the posterior ab wall.
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It was previously thought to be a collection of discrete frameworks – every with different insertions into the posterior wall. However, recent research has found the mesentery to be one contiguous structure, which has led to proposals because that its reclassification together an organ.
In this article, us shall look in ~ the anatomy the the mesentery – that is anatomical structure, vasculature, innervation, lymphatics and also clinical relevance.
Note: Research concerning the mesentery is relatively recent, and also some enlarge textbooks may still define the different parts of the mesentery as different structures – this is currently thought to it is in incorrect.
Fig 1 – streamlined illustration the the mesentery. The acts to connect the little intestine and large intestine come the posterior abdominal muscle wall.
The mesentery has actually several features in the abdomen:Suspends the little and large intestine indigenous the posterior abdominal wall; anchoring them in place, whilst still enabling some movement.Provides a conduit for blood vessels, nerves and also lymphatic vessels.Postulated come play a pathological duty in inflammation diseases such together Crohn’s disease.
The mesentery is developed by a double layered fold of peritoneum.
Although the mesentery is now thought to it is in a contiguous structure, subsections the the mesentery can be named according come the viscera the is linked with. Thus, surname such as mesocolon, mesorectum, mesosigmoid all relate to different parts the the mesentery.
The ‘root’ of the mesentery is the point where the mesentery attaches come the posterior abdominal muscle wall, and also is therefore a ‘bare area’. Due to the selection of abdominal organs the mesentery envelopes, the source is long, narrow and has an tilt orientation, from the left side of the L2 vertebra to the appropriate sacroiliac junction roughly.
In the gastrointestinal tract, there are 6 flexures of note: duodenojejunal, ileocaecal, hepatic, splenic, and also those between the descending and also sigmoid colon and also the sigmoid and also rectum. This flexures are frequently used to mark the distinction between various portions that the mesentery:Mesentery the the tiny intestine – connects the loops that jejunum and also ileum come the posterior abdominal wall and is a mobile structure. (1)Right mesocolon – flattened versus the posterior abdominal wall surface (2)Transverse mesocolon – a mobile structure and also lies between the colic flexures (3)Left mesocolon – flattened against the posterior abdominal wall (4)Mesosigmoid – has a medial part which is flattened versus the posterior abdominal wall, vice versa, the an ar of mesentery connected with the sigmoid colon chin is mobile. (5)Mesorectum – assists in anchoring the rectum with the pelvis.(6)
Fig 2 – little intestine and and big intestine emphasize to show linked mesentery.
The areas of the mesentery that room flattened versus the posterior abdominal wall (the right and left mesocolon and also the medial mesosigmoid) are attached to the abdominal wall via an additional layer that connective tissue recognized as Toldt’s fascia. The fascia includes several lymphatic channels.
Clinical Relevance: minister Volvulus
A volvulus occurs when a loop the intestine twists approximately itself and also its mesentery, leading to obstruction the the bowel. The is feasible that the bowel will twist tightly sufficient to protect against the blood supply to the intestine, and result in bowel infarction.
The many commonly affected area of bowel is the sigmoid colon. The risk of intestinal volvulus is increased in kids with intestinal malrotation, a congenital defect in i beg your pardon the embryological intestinal rotation is incomplete, bring about improper anchoring the the intestines to the posterior abdominal muscle wall.
Medical imaging (abdominal x-ray, CT abdo-pelvis) is commonly used to confirm a diagnosis, and also serious cases require operation intervention.
Fig 3 – ab x-ray demonstrating a sigmoid volvulus
The mesentery acts a conduit because that neurovascular structures.
The superior and inferior mesenteric arteries (SMA and also IMA) arise from the abdominal aorta and also travel in the mesentery to it is provided the abdominal muscle viscera. These vessels likewise give rise to branches the supply the mesentery itself.Superior mesenteric artery – provides the offal of the midgut – from the significant duodenal papilla come the proximal two thirds the the transverse colon.Inferior mesenteric artery – supplies the organs of the hindgut – the distal one third of the transverse colon, splenic flexure, diminish colon, sigmoid colon and also rectum.
The venous drainage of the mesentery is via the exceptional mesenteric vein (SMV) and inferior mesenteric vein (IMV), i m sorry both operation alongside their connected arteries.
Fig 4 – The remarkable mesenteric artery and its branches. Note: the worse pancreatoduodenal artery arises more proximally, and also is not visible top top this illustration.
Fig 5 – significant branches the the inferior mesenteric artery demonstrated in green
The superior mesenteric plexus (a continuation of the celiac plexus) accompanies the exceptional mesenteric artery right into the mesentery.
The superior mesenteric plexus then divides into many secondary plexuses which contain parasympathetic and also sympathetic innervation to the mesentery connected with a certain organ, the guts themselves and also their connected blood vessels.
The mesentery has both lymph nodes and lymphatic vessels. There space several teams of lymph nodes discovered within the mesentery:Inferior mesenteric lymph nodes – obtain lymph native the hindgut organs, and drains into the superior mesenteric lymph nodes.
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Superior mesenteric lymph nodes – receive lymph from the midgut guts (and indigenous the worse mesenteric nodes), and also drains right into the pre-aortic lymph nodes.