Corpus: Posterior intercostal arteries

The posterior intercostal arteries are branches of the thoracic aorta or the superior intercostal artery, supplying blood to the intercostal space.

The posterior intercostal arteries extend from the dorsal to the ventral aspect through the intercostal spaces, with 11 arteries present on each side. The first and second posterior intercostal arteries originate from the superior intercostal artery, a branch of the costocervical trunk of the subclavian artery. These arteries give rise to the dorsal and spinal branches. In contrast, the third to eleventh posterior intercostal arteries branch directly from the thoracic aorta.

On the right side, the posterior intercostal arteries are slightly longer than those on the left because the aorta is situated slightly to the left of the spine. These arteries pass behind the esophagus, the thoracic duct, and the azygos vein, and are covered by the right lung and pleura. On the left side, the posterior intercostal arteries initially make a short dorsal course along the vertebral bodies, covered by the left lung and pleura. The upper two left posterior intercostal arteries are crossed by the superior intercostal vein, while the lower ones are crossed by the hemiazygos vein.

Each posterior intercostal artery divides into several branches. The dorsal branch, also known as the posterior branch, arises from the posterior intercostal artery at the level of the costal collum. This branch travels dorsally between the vertebral body and the costotransversal ligament. The spinal branch diverts from the dorsal branch and passes through the intervertebral foramen into the spinal canal. The dorsal branch further divides into the medial and lateral cutaneous banches. In women, they supply the mammary gland via the lateral mammary branches.

Another important branch of the posterior intercostal artery is the collateral branch, which originates at the costal angulus.

After the dorsal branch, the posterior intercostal arteries follow the costal sulcus along the lower edge of the 3rd to 11th ribs. They run ventrally between the internal and external intercostal muscles and eventually anastomose with the corresponding anterior intercostal arteries as they continue along the ribs.

The posterior intercostal arteries supply blood to the back muscles, intercostal muscles, skin of the back, vertebral bodies, spinal nerves, and mammary glands.

• Anderhuber et al., Waldeyer - Anatomie des Menschen: Lehrbuch und Atlas in einem Band (19. aktualisierte Auflage), De Gruyter, 2012
• Pschyrembel - Arteriae intercostales posteriores, retrieved on 27/01/2023
• Radiopaedia - Posterior intercostal arteries, retrieved on 27/01/2023
• Graumann et al. Anatomie. Schattauer Verlag, 2003