Arteries – Thoracic Vessels

00:01 Welcome to this lecture on arteries and veins of the thoracic cavity.

00:07 This slide lists the objectives that you, as a learner, should be able to answer at the conclusion of this lecture. First, describe the arteries of the thorax, the parent vessels that issue them and then their distribution.

00:23 List the parts of the aorta found in the thorax. Describe the normal and variant branching pattern of the aortic arch. Describe the veins of the thorax, the vessels they empty into and the territory that they drain.

00:43 And then, we’ll move to the summary slide and identify the key take-home messages.

00:49 And then lastly, we’ll provide attribution for the images that are used throughout this presentation. This is our body map and we’ll be focused on the thoracic area and the arteries that lie within and are distributed to the thorax.

01:10 And here’s a posterior view as well as to the area or region that we’ll be covering.

01:19 We’re going to begin with the arteries and the two arteries of interest will be the pulmonary trunk, which we see here issuing from the right ventricle and then we have the aorta as a very close neighbor. So, a little bit about the pulmonary trunk; I don’t have to say a whole lot, it’s not very complicated. Here, again, is our pulmonary trunk, receives blood from the right ventricle so that it can be delivered to the lungs.

01:53 The pulmonary trunk will divide into two pulmonary arteries. This is our left pulmonary artery.

02:01 And then, diving underneath the arch of the aorta is the right pulmonary artery and then, we can see it reappear just to the right of the superior vena cava.

02:16 Now, we’re going to shift to the aorta, the systemic circulation. The aorta has three parts that you should be familiar with. It has an ascending portion that we see right here. It’s receiving blood from the left ventricle. The aorta then will arch superiorly and then will course posteriorly and to the left of the midline and as it does so, it becomes the descending aorta and we see it running behind or posterior to the heart. The descending aorta can be subdivided into a thoracic segment that’s running within the thoracic cavity and then it’ll pass behind the aortic hiatus of the diaphragm and then will enter the abdominal region and become the abdominal segment of the descending aorta.

03:12 When we look at the branching pattern of the aorta, we’ll look at it in its various parts and so, we’ll begin with the ascending aorta. And there are only two arteries that are going to issue from the ascending aorta and those are the arteries that supply the heart. Here, we have the right coronary artery and you can see where it issues from the aorta. And there’s a dilatation at this point in the root of the aorta called the sinus of Valsalva.

03:41 Similarly, we have the left coronary artery issuing from the ascending aorta and there too, is a dilated portion of the aorta called the left sinus of Valsalva. The coronary circulation is described in another lecture and that lecture is titled “The Heart”.

04:04 So, that’ll now bring us to the next part of the aorta and here, we’re going to focus on the aortic arch and its normal branching pattern. And that is demonstrated in the illustration.

04:18 Here is your arch running from here to here. This, then, is the descending aorta. That continues distally. The first branch of the aortic arch is the brachiocephalic trunk and then, it will divide into a right subclavian artery and a right common carotid artery.

04:40 The next branch is the branch that we see here. This will be the left common carotid artery. The common carotid arteries will supply the neck, the head and the brain with the branches that issue distally from them. And then the last branch that we have is the left subclavian artery. The left subclavian and right subclavian arteries will subserve some structures in the inferior part of our neck, will also issue some structures that do supply the thoracic wall and then will continue and are the major arterial suppliers of the upper extremities. The aortic arch is an area of the circulation that is subject to variations in the branching pattern. And we see some variations on this particular slide. Panel B, as we see here, shows your brachiocephalic trunk and then here’s your left common carotid artery. And they are issuing from the same opening within the aortic arch, so they have a common origin in this variation. This occurs in about 13% of the population. Panel C shows yet another type of variation in the branching pattern.

06:06 Here, there’s a common stem and this common stem will give rise to your right subclavian, your right common carotid and then this happens to be your left common carotid. And lastly, we would have the left subclavian artery branching off the arch. This occurs in about 9% of the population. Panel D is a variant pattern that’s seen in about 3% of the population. Here we have four branches: brachiocephalic, left common carotid. This slender branch is the additional branch, the fourth branch; this is the left vertebral artery. And then our last branch is our left subclavian. The most unique variant is the last image that we see.

07:03 Here, we have our right common carotid being the first branch of the aortic arch. We have, then, our left common carotid artery. This is the thyroid ima artery. Here is your left subclavian artery and if you’re keeping track, we have not identified the right subclavian artery, because that is the last branch now that is coming off the aorta and the right subclavian is issuing from the aorta on the left side and it has to make its way to the right side of the body. And it typically will do that by passing behind the esophagus, becoming retroesophageal, or it may run behind the trachea, thus retrotracheal, in order to assume its more normal course on the right side of the body. A very infrequent pattern, but one I have personally been able to see on some occasions. It’s an impressive variation.