Descending Aorta – Thoracic Vessels

00:01 Now, we’ll focus on the descending thoracic aorta. And there are several branches that will issue from this vascular segment. Some of these branches are visceral. We’ll have pericardial arteries. We’ll have bronchial arteries. We’ll have esophageal arteries and then, we’ll have mediastinal arteries that are visceral in nature. We’ll also have some branches that supply the body wall; hence, these are parietal branches. These would include your posterior intercostal arteries, your subcostal arteries, as well as your superior phrenic arteries.

00:43 So, if we take a look at the pericardial arteries, while this diagram or illustration doesn’t demonstrate them to our advantage, we can see the arch of the aorta. The arch again will dive posterior into the left side of the body and now, it’s descending behind the heart and the posterior part of the pericardium that we see and view here. There are two to three small pericardial arteries that will issue, then, from this initial segment of the thoracic descending aorta that will help supply the posterior part of your pericardium as well as posterior mediastinal lymph nodes that are located in this region as well.

01:29 Bronchial arteries: Bronchial arteries will help supply the respiratory passageways and lung tissue with arterial blood that is more fully saturated with oxygen. Certainly, most of the blood flow to the lungs is going to be conveyed through the pulmonary artery system.

01:50 But, we do have some small bronchial arteries that will follow the posterior branching pattern of our respiratory passageways. Those arteries are shown here. If we take a look, here is a posterior view of the descending thoracic aorta. Here is the left main or left primary bronchus going to your left lung and there are two bronchial arteries, left bronchial arteries, that will issue directly from the aorta. On the right side, we only have one right bronchial artery. It does not issue directly from the aorta. Instead, what we have here is the first posterior intercostal artery that issues from the aorta. This one will supply the 3rd posterior intercostal space and as it makes its way into that space, it will give rise to the right bronchial artery. And you just see one coming off and then it will branch and that branching pattern will relate to the branching pattern of your respiratory passageways. So, again, these arteries help supply the bronchi, the lungs. We also have lymph nodes that will be in the vicinity of the bronchi, so lymph nodes are supplied, some small branches to the esophagus. Some small branches from the bronchial arteries will also assist in supplying the pericardium with blood.

03:26 Esophageal arteries are going to be direct branches of the thoracic descending segment of your aorta. Typically, there are four to five of these in number. The esophagus is well endowed with an arterial system. This illustration shows, to our discernment, two esophageal branches. See one here and then we see another one here and the primary structure supplied by these is the esophagus. We also have some small branches and these are numerous small branches. These are mediastinal arteries. These are not discernible. We cannot view them in this particular illustration, but your mediastinal arteries are going to supply structures within the mediastinum. These would include some lymph nodes, nerves and vessels that are within this area of the thoracic cavity and then they’ll help supply the mediastinal pleura that would be associated with the right and left lungs.

04:34 Posterior intercostal arteries: We mentioned earlier that we had the supreme intercostal artery issuing from the costocervical trunk, supplying the first two posterior intercostal spaces. The inferior nine intercostal spaces are going to be supplied by posterior intercostal arteries that are direct branches of the thoracic aorta. And the thoracic aorta has been removed from this image, but the posterior intercostal arteries are still in view. And we see several of those here. And then the last pair that we see here happen to be subcostals. We’ll have all these branches here and then we have some cut ends of the posterior intercostal arteries over in through here. So, these will supply intercostal spaces 3 through 11 and as they travel within the posterior intercostal spaces, they’ll help supply back structures, intercostal structures within the intercostal spaces, such as intercostal muscles. When they approach more anteriorly and laterally, you’ll have pectoral muscular branches. Serratus anterior is also partially supplied by these branches and certainly, the overlying skin and will assist in the arterial supply of the breast.

06:11 Subcostal arteries are going to be branches of the descending thoracic aorta. These relate to the intercostal arteries, but these are going to be located just underneath the 12th rib. So, here, we have one subcostal artery and then, on the opposite side, we have the fellow intercostal artery. For your reference, this happens to be the 12th rib and if we had a 13th rib, which we do not, that, again, would correspond to the relationship that intercostal arteries have. They’ll help supply back structures and as they course laterally and anteriorly, subcostal arteries will also help to supply the anterolateral abdominal wall. The last branches to identify or to point out to you; unfortunately, they’re not seen in this particular illustration. These are superior phrenic arteries. There will be one pair of these issuing from the thoracic aorta before it disappears through the aortic hiatus. So, you have a right one and a left one and they’ll help supply the diaphragm. The arterial supply of the diaphragm is also going to be described more fully in a lecture on the diaphragm.