Intercostal arteries
Arteriae intercostales
Also known as: posterior intercostal arteries, anterior intercostal arteries
The intercostal arteries run in each intercostal space and supply the chest wall. The posterior intercostal arteries come mainly from the thoracic aorta and the anterior intercostal arteries from the internal thoracic and musculophrenic arteries. The two sets join (anastomose) in each space.
Overview
Posterior intercostal arteries. The 1st and 2nd come from the supreme (superior) intercostal artery, a branch of the costocervical trunk. The 3rd to 11th come directly from the thoracic aorta. The subcostal artery runs below the 12th rib. Because the aorta lies to the left, the right posterior intercostal arteries are longer and cross the vertebral bodies behind the oesophagus, thoracic duct and azygos vein.
Each posterior intercostal artery gives a dorsal branch to the back muscles and the spinal cord. One of the spinal branches is usually much larger than the others: the great anterior radiculomedullary artery (of Adamkiewicz). It usually arises on the left between T9 and T12 and supplies much of the lower spinal cord through the anterior spinal artery.
Course in the space. Each artery runs in the costal groove on the underside of a rib, between the internal and innermost intercostal muscles. From above down, the order is vein, artery, nerve (VAN). A smaller collateral branch runs along the upper border of the rib below.
Anterior intercostal arteries. These come in pairs in each space. Spaces 1–6 are supplied by the internal thoracic artery and spaces 7–9 by the musculophrenic artery. The lowest spaces receive only posterior intercostal arteries.
Function
- Supply the intercostal muscles, ribs, overlying skin, parietal pleura and the breast (lateral branches).
- Contribute to the blood supply of the spinal cord through segmental medullary arteries.
Clinical significance
Chest drains and thoracentesis
Needles and chest drains are inserted just above the upper border of the rib below, to avoid the neurovascular bundle in the costal groove. The usual site is the "safe triangle" in the 4th–5th intercostal space in the mid-axillary line.
Spinal cord ischaemia after aortic surgery
Open or endovascular repair of the thoracic or thoracoabdominal aorta can cut off the artery of Adamkiewicz. The result is anterior spinal artery syndrome: paraplegia with loss of pain and temperature sensation, but with proprioception and vibration sense preserved.
Rib notching
In coarctation of the aorta, the posterior intercostal arteries enlarge as bypass routes and erode the undersides of ribs 3–9. Ribs 1 and 2 are spared because their intercostal arteries arise from the costocervical trunk, above the narrowing.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.