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Lymph nodes and vessels of the small intestine and neighbouring structures.
Hello everyone! It's Megan from Kenhub here, and welcome to our tutorial on lymph nodes of the small intestine. Before we begin this tutorial, let's familiarize ourselves with the structure of the small intestine which we can see in this illustration highlighted in green. The small intestine is composed of three parts – the duodenum, the jejunum and the ileum. Superiorly, it's continuous with the stomach and inferiorly, it's continuous with the large intestine.
The lymph nodes of the small intestine are one of the largest group of lymph nodes in the entire body and are important in both the immune system and the lymphatic system. They are also very important clinically as they can be involved in the spread of infections and cancers, therefore, having a knowledge of normal lymphatic drainage will allow you to better understand the potential spread of certain pathologies.
Before we look at the lymph nodes, it's important to understand the basic anatomy of the lymphatic system. So lymph nodes are bean-shaped structures of the lymphatic system that are distributed widely throughout the body and are linked together by lymphatic vessels. Each lymph node has at least one afferent lymphatic vessel and one efferent lymphatic vessel. Vessels that carry lymph towards a lymph node are known as afferent lymph vessels and vessels that carry lymph away from a lymph node are known as efferent lymph vessels. Efferent lymph vessels can carry lymph to a vein into a lymphatic duct or even into another lymph node. So it's important to remember that lymph nodes may receive lymph from both afferent and efferent lymph vessels.
We're going to begin by looking at lymph nodes located near the junction of the ileum of the small intestine and the cecum of the large intestine. This junction is known as the ileocecal junction. The lymph nodes seen in this area are the ileocolic lymph nodes and they drain the distal ileum, the cecum as well as the ascending part of the large intestine. Although there are only two lymph nodes shown in this image, there can be as many as twenty ileocolic lymph nodes. Cancers in these parts of the small and large intestine can spread to these nodes which may result in cancer cells metastasizing to other parts of the body.
As we move proximally along the small intestine, we can see numerous lymph nodes which are known as the juxtaintestinal lymph nodes. These lymph nodes are in close proximity to the small intestines. Specifically, they're close to the arcades and vasa recta of the jejunal arteries and the ileal arteries. Based on their location, you might guessed correctly that these nodes drain lymph from the jejunum and the ileum.
The next group of lymph nodes we're going to look at receives some lymph directly from the small intestine but also receive it from the juxtaintestinal lymph nodes. These are called the intermediate mesenteric lymph nodes and they lie within the mesentery in close proximity to the jejunal and ileal arteries of the small intestine. There are also some lymph nodes located in the right upper portion of the abdomen and they're called the right colic lymph nodes. Although I'm showing you these lymph nodes, it's important to note that they don't drain the small intestine but instead drain the right side of the colon namely the cecum, the ascending colon, and the hepatic flexure.
All of the lymph nodes that we've looked at so far in this tutorial drain into these lymph nodes we can see here which are the superior mesenteric lymph nodes. These nodes drain lymph from the duodenum and are located around the area where the superior mesenteric artery branches off from the abdominal aorta.
So now let's move on to look at the lymphatic drainage of the duodenum. Lymph from the duodenum can drain to many different sites, one of which we actually just mentioned which was the superior mesenteric lymph nodes. However, lymph can also drain to the pancreaticoduodenal lymph nodes which are located near the superior and inferior pancreaticoduodenal arteries.
In this illustration, only one of these lymph nodes is represented; however, there may be many. Please also note that they can drain superiorly into the celiac lymph nodes which we'll talk about next. So here in this illustration we can see the celiac lymph nodes. These lymph nodes are located superior to the superior mesenteric lymph nodes and they surround the celiac trunk which is a major blood supply of the abdominal foregut. Not only do they receive lymph from the duodenum but they can also receive lymph from the superior mesenteric nodes.
Lymph from both the celiac and superior mesenteric nodes drains into this structure seen here which is known as the cisterna chyli. The cisterna chyli is a large lymphatic structure formed by the union of the left lumbar trunk and the intestinal trunk. It drains lymph from the abdomen, the lower limbs and the pelvic organs.
But what exactly is the cisterna chyli? The cisterna chyli is a sac-like expansion of this structure here – the thoracic duct. The thoracic duct is located to the right of the abdominal aorta and receives lymph from the cisterna chyli. It's similar in structure to a medium-sized vein and pierces the diaphragm with the aorta at the level of the twelfth thoracic vertebra. It then continues superiorly through the posterior mediastinum before draining into the left venous angle which lies between the left internal jugular vein and the left subclavian vein.
So that concludes our tutorial on the lymph nodes of the small intestine and should give you a better understanding of the normal drainage of lymph in this region. I hope you enjoyed it and thank you for listening.
Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.
Now, good luck everyone, and I will see you next time.