Now that we’ve seen the bones and muscles of the thorax, we’ll look at the principal blood vessels and nerves of the thoracic region. Of the blood vessels that we’ll look at, there are some that we’ll see only in passing, the pulmonary vessels. These are the major vessels which pass between the heart and the lungs. We’ll see these more fully in Volume Five. We’ll start with the arteries, and we'll begin with the largest artery in the body, the aorta.
Here’s the left pleural cavity with the lung removed, and the heart and mediastinum undisturbed. Here’s the aorta, partly hidden beneath the pleura. It emerges from the left ventricle of the heart, arches over, and runs down alongside the vertebral bodies. It leaves the thorax by passing through the diaphragm, into the abdomen.
To get a better look at the aorta, we’ll remove the overlying pleura, and part of the pericardium that surrounds the heart. We’ll also remove the body of the sternum, and the lower half of the manubrium.
The part of the aorta that lies within the thorax is called the thoracic aorta. It’s spoken of as having three parts, the ascending aorta, the arch, and the descending aorta.
The aorta arises here from the left ventricle. To its left is the pulmonary trunk. To its right is the superior vena cava. The only branches of the ascending aorta are the coronary arteries, which arise just where it starts.
The arch of the aorta makes a complete 180º turn. Beneath the arch of the aorta is the pulmonary trunk, dividing into the two pulmonary arteries: here’s the left one. This is the ligamentum arteriosum. Also beneath the arch are the left main bronchus and the left pulmonary veins. To the right of the arch is the lower end of the trachea.
Before we move on to the descending aorta, we’ll take a look at the three major arteries which arise from the arch. These are the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery.
The brachiocephalic trunk, also known as the innominate artery, divides to form the right subclavian and the right commmon carotid ateries. Here are the origins of these three arteries: brachiocephalic, left common carotid, left subclavian.
Here they are emerging through the upper thoracic aperture. To see them clearly, we’ll remove these veins, the right and left brachiocephalic veins, which unite to form the superior vena cava. We’ll also remove the rest of the manubrium, and the two first ribs, from here to here.
The brachiocephalic artery divides here into the right subclavian and the right common carotid. Here’s the left common carotid, here’s the left subclavian. The subclavian and common carotid arteries are shown in Volumes One and Four respectively.