The posterior intercostal veins are

veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

that drain the

intercostal space The intercostal space (ICS) is the anatomic space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it. Structures in intercostal space * several kind ...

s posteriorly. They run with their corresponding

posterior intercostal artery The intercostal arteries are a group of arteries that supply the area between the ribs ("costae"), called the intercostal space. The highest intercostal artery (supreme intercostal artery or superior intercostal artery) is an artery in the human ...

on the underside of the rib, the vein superior to the artery. Each vein also gives off a dorsal branch that drains blood from the muscles of the back. There are eleven posterior intercostal veins on each side. Their patterns are variable, but they are commonly arranged as: * The 1st posterior intercostal vein,

supreme intercostal vein The supreme intercostal vein (highest intercostal vein) is a paired vein that drains the first intercostal space on its corresponding side. It usually drains into the brachiocephalic vein. Alternatively, it drains into the superior intercostal v ...

, drains into the

brachiocephalic vein The left and right brachiocephalic veins (previously called innominate veins) are major veins in the upper chest, formed by the union of each corresponding internal jugular vein and subclavian vein. This is at the level of the sternoclavicular j ...

or the

vertebral vein The vertebral vein is formed in the suboccipital triangle, from numerous small tributaries which spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas. They unite with small v ...

. * The 2nd and 3rd (and often 4th) posterior intercostal veins drain into the superior intercostal vein. * The remaining posterior intercostal veins drain into the

azygos vein The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blo ...

on the right, or the hemiazygos and

accessory hemiazygos vein The accessory hemiazygos vein, also called the superior hemiazygous vein, is a vein on the left side of the vertebral column that generally drains the fourth through eighth intercostal spaces on the left side of the body. Structure The accessor ...

on the left.

External links

* () * - "Mediastinum: The Sympathetic Ganglion and Sympathetic Trunk" Veins of the torso {{cardiovascular-stub