The vertebral artery or arteria vertebralis in Latin originates from the first part of the subclavian artery in the lower part of the neck. It passes superiorly through the foramina present in the transverse process of the sixth cervical vertebrae, and then curves medially to enter the posterior cranial cavity via the foramen magnum. It is one of the major arteries of the head and neck.
Each vertebral artery can be divided into four parts. The first part runs upwards between the longus colli and scalenus anterior muscles, and behind the common carotid artery and the vertebral vein. It is crossed by the inferior thyroid artery, and by the thoracic duct on the left vertebral and the right lymphatic duct on the right vertebral. Posterior to the artery is the seventh cervical transverse process, the inferior cervical ganglion and the ventral rami of the seventh and eighth cervical spinal nerves.
The second part ascends vertically through the transverse foramina of the sixth till second cervical vertebrae (C6-C2), accompanied by a large branch from the inferior cervical sympathetic ganglion and a plexus of veins that unite in the lower neck to form the vertebral vein.
The third part starts on the medial side of the rectus capitis lateralis muscle, and curves backwards behind the lateral mass of the atlas (C1), with the first cervical ventral spinal ramus lying on its medial side. Here, it settles in the groove found on the upper surface of the posterior arch of the atlas, and enters the vertebral canal below the posterior atlanto-occipital membrane. This part of the vertebral artery is covered by the semispinalis capitis muscle, and lies in the suboccipital triangle. The first cervical or suboccipital nerve separates the artery from the posterior arch of atlas.
The fourth part pierces the dura mater, and ascends anterior to the hypoglossal nerve (CN XII). It then runs downwards to the medulla oblongata, where it unites with its counterpart to form the midline basilar artery at the lower border of the pons.
The third part of the vertebral artery gives off muscular branches that supply the deep muscles of the suboccipital region, and then anastomose with the occipital, ascending and deep cervical arteries. This artery also has additional spinal branches that enter the vertebral canal via the intervertebral foramina and supply: the vertebral bodies, extradural content of the canal, dura, and the spinal cord.
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