The mesentery is a double fold of peritoneal tissue that suspends the small intestine and large intestine from the posterior abdominal wall. This unique anatomical structure was traditionally thought to be composed of a number of distinct structures, each with its own insertion into the posterior wall. However, more recent research has found the mesentery to be a single, continuous structure, which has led to suggestions of it being reclassified as an organ. This article will examine in detail the anatomy of the mesentery, its various functions, associated vasculature and innervation, and its clinical relevance.
The mesentery serves several important functions in the abdomen. Thanks to its double-layered fold of peritoneum, it both suspends the small and large intestine from the posterior abdominal wall, and securely anchors them in place at the same time, allowing for some degree of movement. It also provides a conduit for the passage of blood vessels, nerves and lymphatic vessels, and has been implicated in playing a pathological role in certain types of inflammatory diseases, such as Crohn's disease.
As mentioned previously, the mesentery is now thought to be one single, uninterrupted structure. However, for ease of description, subsections of the mesentery can still be named according to the particular viscera they are associated with - such as the mesocolon, mesorectum and mesosigmoid.
The 'root' of the mesentery is the point at which it attaches to the posterior abdominal wall. This area is otherwise known as a 'bare area', and is long, narrow, and has an oblique orientation, running from the left side of the L2 vertebra to the right sacroiliac joint. Furthermore, within the gastrointestinal tract, there are six distinct flexures - duodenojejunal, ileocaecal, hepatic, splenic, and those between the descending and sigmoid colon, and the sigmoid and rectum.
When a loop of intestine twists through itself and its mesentery, this can lead to a condition known as volvulus. If this twist is particularly tight, it can prevent the blood supply from being able to reach the intestine, leading to a process known as bowel infarction. The sigmoid colon is the area of the bowel most commonly affected by this condition. The risk of volvulus is increased in children with a congenital defect known as intestinal malrotation, in which the organ has an incomplete, embryonic rotation, resulting in improper anchoring to the posterior abdominal wall.
Medical imaging, such as abdominal x-rays or CT scans, is used to confirm diagnosis of these issues, and more serious cases may require surgical intervention.
The mesentery is an anatomical structure that originates from the peritoneum that connects and suspends abdominal viscera and is composed of two layers, the parietal and visceral layers.
Its purpose is to connect the abdominal viscera, connect the abdominal cavity to the abdominal wall, support the fascia, enable the flexion of the abdominal viscera and provide support for the intestinal organs. The mesentery also has a complex structure that includes the vasculature, lymphatics, and innervation.
The superior and inferior mesenteric arteries and their corresponding veins provide arterial and venous circulation through the mesentery. The superior mesenteric artery supplies the midgut organs, from the major duodenal papilla to the proximal two thirds of the transverse colon, while the inferior mesenteric artery supplies the hindgut organs, the distal one third of the transverse colon, the splenic flexure, descending colon, sigmoid colon, and rectum.
The inferior mesenteric lymph nodes receive lymph from the hindgut organs and drain into the superior mesenteric lymph nodes, which then receive lymph from the midgut organs and from the inferior mesenteric nodes before finally draining into the pre-aortic lymph nodes.
The superior mesenteric plexus, which is a continuation of the celiac plexus, accompanies the superior mesenteric artery into the mesentery. This plexus then divides into many secondary plexuses which contain parasympathetic and sympathetic innervation to the mesentery associated with a particular organ, the organs themselves, and their related blood vessels.
The mesentery flexures are often used to mark the distinction between different portions of the mesentery. Mesentery of the small intestine connects the loops of jejunum and ileum to the posterior abdominal wall and is a mobile structure. The right mesocolon is flattened against the posterior abdominal wall, the transverse mesocolon is a mobile structure and lies between the colic flexures, and the left mesocolon is also flattened against the posterior abdominal wall. The mesosigmoid has a medial portion which is flattened against the posterior abdominal wall, whereas the region of mesentery associated with the sigmoid colon itself is mobile. Lastly, the mesorectum assists in anchoring the rectum through the pelvis.
The areas of the mesentery that are flattened against the posterior abdominal wall (the right and left mesocolon and the medial mesosigmoid) are attached to the abdominal wall via an additional layer of connective tissue known as Toldt’s fascia. This fascia contains several lymphatic channels.
A volvulus occurs when a loop of intestine twists around itself and its mesentery, causing obstruction of the bowel. It is possible that the bowel will twist tightly enough to prevent the blood supply to the intestine and result in bowel infarction. The most commonly affected area of bowel is the sigmoid colon.
The risk of intestinal volvulus is increased in children with intestinal malrotation, a congenital defect in which the embryological intestinal rotation is incomplete, resulting in improper anchoring of the intestines to the posterior abdominal wall. Medical imaging (abdominal x-ray, CT abdo-pelvis) is frequently used to confirm a diagnosis, and serious cases require surgical intervention.
The mesentery is a complex structure that serves multiple vital functions, including connecting the abdominal viscera, connecting the abdominal cavity to the abdominal wall, supporting the fascia, enabling the movement and flexion of the abdominal viscera and providing support for the intestinal organs.
It contains the superior and inferior mesenteric arteries and their corresponding veins for arterial and venous circulation, as well as the superior mesenteric plexus, which provides parasympathetic and sympathetic innervation to the mesentery and its associated viscera. The mesentery also contains lymph nodes and lymphatic vessels to act as a conduit for the lymphatic system.
The mesentery has clinical relevance and plays an important role in disease processes like intestinal volvulus, intestinal malrotation, and the medical imaging of abdominal pathology. Understanding the structure and function of the mesentery is an important part of providing effective medical care and helping to prevent and treat abdominal pathology.
The mesentery is a part of the gastrointestinal tract which begins at the duodenojejunal (DJ) flexure, and extends down to the ileocaecal flexure, hepatic flexure, splenic flexure, sigmoid colon flexure, and finally the rectum. Its outer surface is covered by a fibrous tissue known as Toldt’s fascia (or simply, the mesenteric fascia).
Historically, the mesentery was thought to be an agglomeration of separate anatomical components. It was only in the 21st century that scientists fully recognized it as a single organ.
The mesentery is made up of several layers. These include the serosa (or adventitial layer), the muscle layer, and the mucosa (or submucosa). Each of these layers has important functions in the body that work together to provide the important organ with its necessary functionality.
The serosa is the outermost layer of the mesentery and is comprised of connective tissues, which protect the mesenteric fascia from damage. The next layer, the muscle layer, consists of smooth muscles that aid digestion by helping to mix and move materials through the gastrointestinal tract. The mucosa is the innermost layer, and it is composed of mucous membranes that secrete digestive enzymes and help to break down food for absorption.
In order to understand how the mesentery functions, one must first understand what it is connected to. The mesentery attaches to the small intestine, which is used to absorb nutrients from food, and the large intestine, which absorbs water, and eliminates waste from the body. Additionally, it is responsible for attaching the abdominal organs, such as the liver, pancreas, and spleen, to the abdominal wall.
The mesentery plays an important role in digestion. It helps move food through the digestive tract, facilitating the absorption of nutrients, and it acts as a conduit for the movement of fluids, hormones, and other necessary substances throughout the body. Additionally, the mesentery is responsible for supporting the sigmoid colon and preventing it from becoming kinked.
The mesentery also helps to protect the organs. Its strong, fibrous structure helps to support and protect the intestines and other abdominal organs, preventing them from becoming damaged or displaced. Additionally, the mesentery also serves as an anchor for the blood vessels which supply the intestines with oxygen and other necessary nutrients.
The mesentery is a vital organ, and its importance cannot be overstated. It plays a crucial role in digestion and absorption of nutrients, as well as in the prevention of damage to the abdominal organs. Without it, digestion would be inefficient, and the organs would be at risk of injury or displacement.
Unfortunately, the mesentery has been largely overlooked for many years, and its importance is only now becoming more widely recognized within the scientific community. As medical science continues to advance, scientists are learning more and more about this important organ, and its importance in the overall functioning of the body.
