Vertebral Artery

• The vertebral artery is one of the two principal arteries which supply the brain. 
• In addition, it also supplies the spinal cord, the meninges, and the surrounding muscles and bones. 
• It arises from the posterosuperior aspect of the first part of the subclavian artery near its commencement. 
• It runs a long course, and ends in the cranial cavity by supplying the brain. 
• The artery is divided into four parts

First Part

• The first part extends from the origin of the artery (from the subclavian artery) to the transverse process of the sixth cervical vertebra.
• This part of the artery runs upwards and backwards in the triangular space between the scalenus anterior and the longus colli muscles called as the scalenovertebral triangle

Relations

Anterior

1. Carotid sheath with common carotid artery

2. Vertebral vein

3. Inferior thyroid artery

4. Thoracic duct on left side.

Posterior

1. Transverse process of 7th cervical vertebra 

2. Stellate ganglion

3. Ventral rami of nerves C7, C8.

Second Part

The second part runs through the foramina transversaria of the upper six cervical vertebrae. 

Its course is vertical up to the axis vertebra. 

It then runs upwards and laterally to reach the foramen transversarium of the atlas vertebra.

Relations

1. The ventral rami of second to sixth cervical nerves lie posterior to the vertebral artery.

2. The artery is accompanied by a venous plexus and a large branch from the stellate ganglion

Third Part

Third part lies in the suboccipital triangle. 

Emerging from the foramen transversarium of the atlas, the artery winds medially around the posterior aspect of the lateral mass of the atlas. 

It runs medially lying on the posterior arch of this bone, and enters the vertebral canal by passing deep to the lower arched margin of the posterior atlanto-occipital membrane.

Relations

Anterior: Lateral mass of atlas.

Posterior : Semispinalis capitis.

Lateral: Rectus capitis lateralis.

Medial: Ventral ramus of the first cervical nerve.

Inferior:

1. Dorsal ramus of the first cervical nerve

2. The posterior arch of the atlas

Fourth Part

1. The fourth part extends from the posterior atlantooccipital membrane to the lower border of the pons.

2. In the vertebral canal, it pierces the dura and the arachnoid, and ascends in front of the roots of the hypoglossal nerve. 

3. As it ascends, it gradually inclines medially to reach the front of the medulla.

4. At the lower border of the pons, it unites with its fellow of the opposite side to form the basilar artery

BRANCHES OF VERTEBRAL ARTERY

First part has no branches.

Cervical Branches

1. Spinal branches from the second part enter the vertebral canal through the intervertebral 

foramina, and supply the spinal cord, the meninges and the vertebrae.

2. Muscular branches arise from the third part and supply the suboccipital muscles.

Cranial Branches

These arise from the fourth part. 

They are:

1. Meningeal branches

2. The posterior spinal

3. The anterior spinal artery

4. The posterior inferior cerebellar artery

5. Medullary arteries

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Vertebral Artery | Origin| Termination| Parts| Course| Relations|Branches| Subclavian Steal Syndrome