vertebral artery n.
The first branch of the subclavian artery, divided into four parts: the prevertebral part, before it enters the foramen of the transverse process of the sixth cervical vertebra; the transverse part, in the transverse foramina of the first six cervical vertebrae; the atlas, running along the posterior arch of the atlas; and the intracranial part, within the cranial cavity to union with the artery from the other side to form the basilar artery.