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Main arteries of the trunk

Major arteries of the thorax, abdomen and back.

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Hey everyone! This is Nicole from Kenhub, and in this video, we're going to look at the blood supply to the trunk.

So, in this tutorial, we're going to cover the thoracic aorta, the celiac trunk, the superior mesenteric artery, the inferior mesenteric artery, and the common iliac arteries and their associated branches. But before we begin, we're just going to have a bit of a talk through the circulatory system.

So, in this image, we're having a look at the heart and some of the major arteries making up the circulatory system. The circulatory system is the main transportation system of the body and it's made up of three types of vessels: arteries, veins and capillaries. The vessels are filled with blood carrying gases, nutrients and wastes and in this tutorial, we're only going to be looking at the arteries. The arteries being the vessels that bring oxygenated blood away from the heart to the rest of the body. So, let's just take a couple of minutes to discuss briefly how we're going to talk about blood flow today.

So, in studying anatomy, it's always better to consider the relationships between structures rather than memorizing them individually as memorizing them individually probably will take a really long time and most likely it will be really difficult to remember. So, it's better that we talk about relationships, and throughout this tutorial, we're going to follow the pattern of blood flow from one artery to the next to show how blood cells move through the body after they leave the heart. We're going to start, of course, with the largest artery in the body which is the aorta as oxygenated blood leaves the heart through the aorta to enter systemic circulation.

The aorta is divided into three parts – the ascending aorta, the arch of the aorta and the descending or the thoracic aorta – and now, we're going to look at them in a little bit more detail.

We're going to begin, of course, with the ascending aorta which you can now see highlighted in green. The ascending aorta receives richly oxygenated blood from the left ventricle of the heart transmitted by the appropriately named aortic valve. And in this illustration, we can also see most of the other great vessels arriving or departing from the heart, for example, the inferior and superior vena cavae, the pulmonary trunk, and the left pulmonary veins.

Removing the great vessels for a moment, we can now see the initial portion of the ascending aorta just superior to the aortic valve and from here, two small yet extremely important arteries are given off and these are known as the right and left coronary arteries.

The left coronary artery usually arises immediately superior to the left coronary leaflet of the aortic valve and it continues as the left coronary artery proper only for about ten to fifteen millimeters before dividing into its two primary branches – a circumflex branch and an anterior interventricular branch. The circumflex branch follows a route along the left part of the coronary sulcus wrapping around the circumference of the heart to its posterior aspect. The anterior interventricular branch of the left coronary artery also commonly known as the left anterior descending artery courses in a superior to inferior direction along the anterior interventricular sulcus.

The right contrary artery arises from the opposite side of the aortic hiatus just above the right coronary leaflet of the aortic valve and it continues along the right portion of the coronary sulcus giving off several branches before terminating as the posterior interventricular artery.

If any of the coronary arteries becomes blocked, a person may suffer a myocardial infarction more commonly called a heart attack.

So, over here, we're looking at the aorta on the posterior wall of the thorax. We can still see the trachea and the esophagus and the arch of the aorta which is highlighted in green is the second part of the thoracic aorta and has three major branches that supply blood to the head, neck and the upper limbs. First branch of this is the brachiocephalic trunk, and this artery will split into the right subclavian artery supplying the right upper limb and the right common carotid artery supplying the head and the neck.

The next branch slightly behind and to the left is the left common carotid artery and this also supplies the head and the neck. The last branch is the left subclavian artery and this supplies the left upper limb. So blood that doesn’t enter one of these three branches will continue traveling down the aorta through the thorax and into the abdomen. Blood from the arch of the aorta flows directly into the descending or thoracic aorta and we're looking at this part of the aorta in situ – how we would find it in the body.

So, here's the arch of the aorta with its branches. We can also see the trachea, and these over here are some of the muscles that move the ribs. The thoracic aorta is highlighted in green and branches from the thoracic aorta are fairly straightforward. Over here are some small paired branches that project laterally just below each rib and these are the posterior intercostal arteries and they supply the ribs and the muscles that move them. The word "costal" refers to the ribs and "inter" means that the arteries are located in the spaces between two ribs and the artery that travels below the twelfth rib has a special name and that name is the subcostal artery.

In this image, we're looking at the inferior surface of the diaphragm and highlighted in green, we can see the abdominal aorta which is the name that the artery obtains when entering the abdominal cavity. These are ribs, and the spinal column is back here. These are the arteries and the nerves that supply the diaphragm so blood in the thoracic aorta continues traveling inferiorly towards the diaphragm and enters the abdomen through the hiatus or the hole in the muscle. And from this perspective, we can see the aorta passing through the aortic hiatus.

So, this is the abdomen with the digestive organs removed, and with these organs out of the way, we can see the kidneys and major blood vessels on the posterior abdominal wall. The abdominal aorta is highlighted in green and I'll point out the major arterial branches in the abdomen from here and then we'll look at the unpaired branches more closely.

So just beneath the diaphragm is the celiac trunk and below that is the superior mesenteric artery and below that, the renal veins. Just behind these veins, we can see a little bit of the renal arteries going to the kidneys and over here are the gonadal arteries that supply either the ovaries or the testes, and finally, this is the inferior mesenteric artery.

The celiac trunk is the first major artery beneath the diaphragm. Because the abdominal aorta is on the posterior abdominal wall, we have to retract some of the abdominal organs to see it. Here, we have moved the liver and the stomach, and the celiac trunk is a short artery – just this part highlighted in green – and divides almost immediately into three smaller branches that supply the digestive organs. Here, we have the left gastric artery, the splenic artery and the common hepatic artery. And fun fact, although it's very rare, there have been some reports of patients who have no celiac trunk and in those cases, the three branches arose immediately from the aorta.

Okay, so we've put most of the digestive organs back in the body now and here's the duodenum, the small intestines and part of the large intestines. And below the celiac trunk is another unpaired artery – the superior mesenteric artery shown here in green. And this is called a mesenteric artery because its branches travel through a mesentery attached to the intestines. The superior mesenteric artery supplies the small intestines and the first part of the large intestines.

With the small intestines back in the body, we can see the superior mesenteric artery passing over the duodenum. Interestingly, if the abdominal wall is weakened in some way and the small intestines are not supported, the superior mesenteric artery can be pulled down along with them. This compresses the duodenum and can cause a painful obstruction. Now, as you can see in this image, we've moved a bit inferior but we can still see the duodenum and the superior mesenteric artery.

Our final unpaired branch is the inferior mesenteric artery which is here in green. And this small artery provides blood supply to the last part of the large intestines and the rectum.

As the aorta approaches the pelvis, it bifurcates or splits into the right and left common iliac arteries. Each common iliac artery bifurcates again to form the internal and external iliac arteries and these arteries supply the pelvis and the lower limb. Changes in the diameter of arteries can cause serious complications.

So now that we've finished talking about the arteries of the trunk, let's talk a little bit about some clinical notes that are associated with the arteries.

So, one of the major problems that we see in many patients, of course, is atherosclerosis, which is a condition in which plaques build up along the arterial walls, and in doing so, this constricts the lumen. So, what happens in atherosclerosis is that the walls of the artery become hard and blood flow becomes restricted. If blood flow is completely blocked in one of the coronary arteries supplying the heart walls, the patient will, of course, suffer a heart attack.

Something else we want to talk about is an aneurysm, and an aneurysm on the other hand is an abnormal widening of a weak arterial wall. And if the wall bulges too much, your blood pressure becomes too high, the weakened wall can burst. So, aneurysms can occur in any vessel but are most frequently seen in the basilar artery and in the aorta.

So thanks for sticking with me throughout this tutorial. I hope you've learned a little bit more about the blood flow of the arteries of the trunk. Now that we've reached the end, let's just go over what we talked about today.

So, in this video, we looked at the major arteries supplying the abdomen and the thorax and we began by looking at the major parts of the aorta. Firstly, we looked at the ascending aorta which arises immediately off the heart and has two small branches that supply the heart walls with blood. Then we looked at the arch of the aorta which curves backwards towards the vertebral column and gives rise to some of the great vessels of the heart. The descending aorta then courses inferiorly through the thorax and the abdomen.

In the abdomen, we then looked at some of the specific branches of the aorta which included the renal arteries which supply the kidneys on the posterior wall of the abdomen, the celiac trunk which has many smaller branches that supply organs involved in digestion like the stomach and the pancreas, the superior mesenteric artery which arises a little below the celiac trunk and supplies most of the small intestines, and the inferior mesenteric artery which is the most inferior unpaired branch and supplies the large intestines. Then we looked at the most inferior part of the aorta which bifurcates into two other arteries – the right and the left common iliac arteries and these will go on to bring blood to the pelvis and to the lower limbs.

And now as we exit the trunk, it's time to finish our tutorial. Thanks for watching and happy studying!

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