Posterior intercostal arteries

At a glance

English

Posterior intercostal arteries

Latin (TA2)

Arteriae intercostales posteriores

System

Artery

Region

Trunk

Side

Paired, left and right

About the posterior intercostal arteries

Each side has eleven of these arteries, one for every intercostal space. The first two come from the supreme (highest) intercostal artery, which the subclavian artery gives off by way of its costocervical trunk. The remaining nine leave the back of the descending thoracic aorta and are called the aortic intercostals. Below the twelfth rib the series is completed by the subcostal artery.

Because the aorta lies to the left of the vertebral column, the right arteries are longer. They cross the front of the vertebral bodies behind the oesophagus, the thoracic duct and the azygos vein, with the right pleura and lung over them. The left arteries pass backwards along the flanks of the vertebral bodies beneath the left pleura and lung; the hemiazygos vein crosses the lower ones, while the highest pair lie beneath the left superior intercostal vein. Close to each rib head the sympathetic trunk descends in front of them, and lower down the splanchnic nerves also pass in front.

Close to the rib head each artery gives a dorsal branch that runs back to the deep muscles and skin of the back and sends a spinal branch through the intervertebral foramen to the vertebra, the meninges and the spinal cord; some of these feed the segmental medullary arteries of the cord. The main stem then enters the costal groove under its rib, between the internal and innermost intercostal muscles. Within the groove the vein lies highest, the artery in the middle and the nerve lowest. A collateral branch runs along the top of the rib below, and further forward both join the anterior intercostal branches of the internal thoracic and musculophrenic arteries. Lateral cutaneous branches supply the skin of the side of the chest.

Because the bundle hugs the lower border of each rib, needles and chest drains are passed just above the upper edge of a rib. In coarctation of the aorta these arteries enlarge to carry blood round the narrowing and notch the lower borders of the ribs on a chest X-ray. Their spinal branches matter in aortic surgery, where loss of them can endanger the cord.

Course and supply

Arises from

The first and second from the supreme intercostal artery of the costocervical trunk; the third to eleventh from the back of the descending thoracic aorta.

Ends in

Each divides into a dorsal branch and an intercostal stem that runs forwards in the costal groove to join the anterior intercostal branches of the internal thoracic or musculophrenic artery.

Supplies

Supply the intercostal muscles, ribs, parietal pleura, overlying chest wall skin and muscles, the deep back muscles, the vertebrae and, through spinal branches, the spinal cord and its coverings.