Major Vessels of the Thoracic Cavity

Superior vena cava system

The formation of the venous bed of the upper floor of the thoracic cavity begins with the brachiocephalic veins (venae brachiocephalicae). They are formed behind the sternoclavicular joints by the confluence of the internal jugular and subclavian veins. The right and left veins have distinct topographical differences:

• The right brachiocephalic vein is significantly shorter than the left. It has an almost vertical course and is projected strictly onto the right margin of the manubrium sterni.
• The left brachiocephalic vein is approximately twice as long as the right. It crosses the mediastinum obliquely from left to right behind the manubrium sterni, and its projection corresponds to the level of attachment of the cartilages of the first (less commonly second) rib.

The confluence of these two veins forms the superior vena cava (vena cava superior). The vessel is projected along the right margin of the sternum from the 1st to the 3rd rib. The venous trunk protrudes beyond the right margin of the sternum by approximately half of its diameter. Anatomically, the mouth of the vein lies at the border between its lower and middle thirds. Almost the entire surface of the vessel is covered by the pericardium, except for a small posterior segment.

The syntopy of the superior vena cava is quite complex. Anteriorly, the left brachiocephalic vein is covered by the thymus, and on the right, the vascular bundle is covered by the mediastinal pleura. Posterior to the vein lie the trachea, the brachiocephalic trunk, and partially the left common carotid artery. In the middle third, the azygos vein (v. azygos) empties into the posterior wall of the vessel. Important landmarks are the nerves: the right vagus nerve passes posterior to the superior vena cava, and the right phrenic nerve descends along its right wall.

Topography of the aortic arch and thoracic aorta

The aortic arch (arcus aortae) serves as the direct continuation of the ascending aorta. Topographically, it originates at the level of attachment of the 2nd rib cartilage to the left margin of the sternum, reaches its highest point behind the center of the manubrium sterni, and, turning to the left, continues into the descending part at the level of the 4th thoracic vertebra.

Anteriorly, the initial and terminal segments of the arch are covered by the costomediastinal pleural recesses, while the middle section is covered by adipose tissue and the thymus. The posterior surface of the arch forms an impression on the anterior wall of the trachea. The left vagus nerve lies adjacent to the left surface of the arch, from which the left recurrent laryngeal nerve branches off, characteristically looping around the arch inferiorly and posteriorly. Lateral to the vagus nerve lies the left phrenic nerve.

Three large vessels successively branch off from the superior semi-circumference of the aortic arch:

1. The brachiocephalic trunk (truncus brachiocephalicus) is the first branch. It runs upwards and to the right, separated from the sternum by the left brachiocephalic vein and neck muscles. At the level of the right sternoclavicular joint, it divides into the right common carotid and subclavian arteries.
2. The left common carotid artery arises to the left and slightly posterior to the brachiocephalic trunk.
3. The left subclavian artery is located even further posteriorly and is partially covered by the pleura.

The thoracic aorta (pars thoracica aortae) runs in the posterior mediastinum along the bodies of the 4th–12th vertebrae. Anterior to it are the root of the left lung and the esophagus, which crosses the aorta from right to left. Posteriorly lies the hemiazygos vein. This entire section is enclosed in a dense fascial sheath firmly fused with the adventitia, prevertebral fascia, and pleura.

Pulmonary trunk and ligamentum arteriosum

The pulmonary trunk (truncus pulmonalis) is completely hidden within the pericardial cavity. It originates at the level of attachment of the cartilage of the left 3rd rib to the sternum and is located anterior and to the left of the ascending aorta. Having ascended to the level of the upper margin of the cartilage of the left 2nd rib, the trunk divides into the right and left pulmonary arteries.

An important anatomical structure in this zone is the ligamentum arteriosum (lig. arteriosum), which is the obliterated ductus arteriosus. It attaches from the inferior surface of the aortic arch (at the level of origin of the left subclavian artery) to the wall of the pulmonary trunk in the area of its bifurcation. From a clinical perspective, it is important to remember that the left phrenic nerve runs only 1–2 cm anterior to this ligament, serving as a reliable surgical landmark.

Class and exam questions

What else to study on this topic

• Syntopy of the vagus and phrenic nerves in the mediastinum
• Fascial bed of the thoracic aorta and its connections with surrounding tissues
• Topographical relationships of the thoracic aorta and esophagus at the level of the 7th–10th vertebrae
• Variant anatomy of the branching from the aortic arch (e.g., origin of the vertebral artery)

Other topics in the section "Topographic Anatomy of the Chest"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.