The vertebral artery is a paired blood vessel that lies deep in the neck region. It is the first branch of the subclavian artery and it supplies the brain together with the internal carotid artery. It arises from the postero-superior side of first portion of the subclavian. Then the vertebral artery runs upwards, and slightly backwards, behind the common carotid artery along the lateral border of the longus cervicis muscle. Next, it enters the foramen transversarium of the sixth cervical vertebra and ascends vertically through the openings in the transverse processes of all the other cervical vertebrae. At the level of the medulla, the right and left vertebral arteries come together and merge into one single blood vessel; the basilar artery.
On emerging from the foramen transversarium of the first cervical vertebra (atlas), the vertebral artery runs medially on the groove of the upper surface of the atlas. Then it turns upwards, entering the cavity of the skull through the foramen magnum, piercing the dura mater. In the cavity of the cranium, the right and left vertebral arteries converge into one artery on the surface of the medulla oblongata to become the basilar artery, which is a short blood vessel. On the surface of the pons, the basilar divides into the two posterior cerebral arteries, which are part of the circle of Willis.
The vertebral artery is usually divided into four parts: 1) the pre-vertebral part, which is the portion before it enters the foramen transversarium of the sixth cervical vertebra; 2) the transversarial part, which the portion of the blood vessel running through all six foramen transversaria of the first six cervical vertebrae; 3) sub-occipital atlantic part, which is the portion running along the posterior arch of the atlas (first cervical vertebra); and 4) intracranial part, which is the last section of the blood vessel lying within the cranial cavity where it meets the artery from the other side.
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| Above, the vertebral artery arising from first portion of right subclavian. |
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| Side view of vertebral artery running up through cervical foramen transversaria. |