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Arteries of the small intestine with focus on the superior mesenteric artery.
Hello everyone! It's Megan from Kenhub here, and welcome to our tutorial on the arteries of the small intestine. During this tutorial, we will mainly be focusing on the image you can now see in front of you which is an anterior view of the abdominal cavity. In this image, the abdominal wall and some organs such as the transverse colon, the pancreas and the stomach have been dissected away. This has been done to give us a better view of the small intestine and its blood supply. We will start off by looking at a few arteries in this area which don't supply the small intestine. You may wonder we're doing this but these arteries are in close proximity to the small intestine so they're important to know about.
The first artery we'll look at is the splenic artery. Here we can see the start of the abdominal aorta after it pierces the diaphragm. The first main artery that branches off the abdominal aorta is the celiac artery which then gives off three of its own branches. The one branch into the left here is the splenic artery. This artery is the largest branch of the celiac artery and it supplies the spleen which is this organ here. The smallest branch of the celiac artery is the left gastric artery. This artery branches off to the left hand side of the body to supply the esophagus and the stomach. The final branch of the celiac artery is the common hepatic artery. As you can see, there is a branch coming off this artery which is known as the gastroduodenal artery.
So let's take a closer look at the gastroduodenal artery. This artery supplies both the stomach as well as the small intestine specifically the first part which is called the duodenum. The gastroduodenal artery ends here at this bifurcation where it splits into two arteries. The artery highlighted in green is known as the superior anterior pancreaticoduodenal artery. The superior anterior pancreaticoduodenal artery supplies the anterior part of the duodenum and the head of the pancreas. Although we can't see it in this image, there's also a posterior superior pancreaticoduodenal artery which supplies the posterior part of the duodenum and the pancreas.
The other branch of the bifurcation of the gastroduodenal artery is the right gastro-omental artery. It's also commonly called the right gastroepiploic artery. We can only see part of the artery here but it supplies the stomach and the greater omentum. After the common hepatic artery gives off the gastroduodenal artery, it continues as the proper hepatic artery which we can see here highlighted in green. This artery is also known as the hepatic artery proper. It runs alongside the common bile duct and supplies the liver.
The next main artery that branches off the abdominal aorta is the left renal artery. The left renal artery branches off the left hand side of the abdominal aorta a bit lower than the right renal artery which branches off from the right hand side. The renal arteries supply both of the kidneys and here we can see the left renal artery supplying the left kidney.
The next artery that branches off the abdominal aorta is the superior mesenteric artery. This artery branches off anteriorly at the level of the intervertebral disc between the first and second lumbar vertebrae. It can be seen crossing the front of the horizontal part of the duodenum and it supplies most of the small intestine as well as the cecum and the ascending colon. One of the first branches of the superior mesenteric artery is this one here – the inferior pancreaticoduodenal artery. This artery branches off the right side of the superior mesenteric artery and supplies the head of the pancreas as well as the duodenum. This artery bifurcates into anterior and posterior branches which anastomose with the corresponding superior pancreaticoduodenal branches of the gastroduodenal artery.
The next part of the small intestine – the jejunum – is supplied by five to ten branches which arise from the left hand side of the superior mesenteric artery. These branches are known as the jejunal arteries. As you can see, these arteries form a series of loops or arches which are called the arterial arcades. Such a configuration of arterial structures ensures that the jejunum will keep receiving its blood supply even if some jejunal branches are injured or occluded.
There are also a group of arterial arcades that supply the ileum – the final part of the small intestine. These are called the ileal arteries. Again, this structure ensures the continuous blood supply to the ileum even in cases of occlusion or injury of the blood vessels. Coming off from the arcades of the jejunal and ileal arteries are these arteries here which are called the straight arteries. They are also sometimes known as the vasa recta which, funnily enough, is Latin for "straight arteries".
Now if we look at the right side of the superior mesenteric artery, we can see this large branch here which is called the ileocolic artery. The ileocolic artery is generally considered to have four branches. One of these branches is the ileal branch. As we can see, this branch supplies the lower part of the ileum. The next branch of the ileocolic artery is the anterior cecal artery. This artery supplies the anterior part of the cecum – the first part of the large intestine. What we can see in this image is a rare variation of the origin of the anterior cecal artery. The anterior cecal artery normally arises from the colic branch of the ileocolic artery along with the posterior cecal artery whereas, here, we can see it arising from the ileal branch of the ileocolic artery.
The cecum is supplied by another branch of the ileocolic artery called the posterior cecal artery. This artery supplies the posterior aspect of the cecum and although we can't see it in this image, this artery also gives off a branch that supplies the appendix called the appendicular artery.
The final branch of the ileocolic artery is known as the colic branch. Remember that the anterior cecal artery normally arises from this artery. This branch supplies the ascending colon – the next part of the large intestine. The colic branch of the ileocolic artery anastomoses via the ascending branch with this artery here – the right colic artery. The right colic artery also supplies the ascending colon. In this image, this artery can be seen branching off the right side of the superior mesenteric artery but it may also branch off the ileocolic artery or the middle colic artery.
The last artery we'll look at is the middle colic artery. It's been mostly dissected away from this image but we can see a tiny bit of it here. The middle colic artery branches from the front surface of the superior mesenteric artery and it supplies the transverse colon most of which has also been dissected away but we can see the first part of it here.
So now let's go over why the arterial blood supply of the small intestine is good to know in clinical practice. The superior mesenteric artery constitutes the main blood supply of the small intestine and can rarely become blocked. This is known as superior mesenteric artery occlusion. This usually occurs due to an embolus blocking the artery or due to atherosclerosis. Occlusion of the superior mesenteric artery can lead to a condition known as mesenteric ischemia. This is a life threatening condition and can cause the small intestine to become gangrenous which means that the tissues die. The patient presents with severe abdominal pain and, possibly but not always, a history of abdominal pain associated with meals, diarrhea and weight loss.
Atrial fibrillation is a common aspect of the patient's history and may be present on examination. The main finding of this condition is a relatively normal abdominal examination despite severe abdominal pain. In a third of cases, patients complain or present with watery or bloody diarrhea. Mesenteric ischemia also presents with nausea, vomiting and change in bowel habit. If abdominal tenderness and guarding are present, one should be wary of the possibility of small bowel gangrene and perforation. Early treatment is essential and usually involves both thrombolytics and surgical intervention.
So that brings us to the end of our tutorial on arteries of the small intestine. I hope you enjoyed it and thank you for listening.
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Now, good luck everyone, and I will see you next time.