The branches of the subclavian artery and the course of the vertebral artery in the neck (schematic).
The three major arteries of the cerebellum: the SCA, AICA, and PICA. (Vertebrals labeled at bottom.)
The vertebral arteries are major arteries of the neck. They branch from the subclavian arteries and merge to form the single midline basilar artery in a complex called the vertebrobasilar system, which supplies blood to the posterior part of the circle of Willis and thus significant portions of the brain.
The vertebral arteries arise from the subclavian arteries, one on each side of the body, then enter deep to the transverse process of the level of the 6th cervical vertebrae (C6), or occasionally (in 7.5% of cases) at the level of C7. They then proceed superiorly, in the transverse foramen (foramen transversarium) of each cervical vertebra. Once they have passed through the transverse foramen of C1 (also known as the atlas), the vertebral arteries travel across the posterior arch of C1 and through the suboccipital triangle before entering the foramen magnum.
Inside the skull, the two vertebral arteries join to form the basilar artery at the base of the medulla oblongata. The basilar artery is the main blood supply to the brainstem and connects to the Circle of Willis to potentially supply the rest of the brain if there is compromise to one of the carotids. At each cervical level, the vertebral artery sends branches to the surrounding musculature via anterior spinal arteries.
The branches of the subclavian artery are: 1. Vertebral; 2. Internal mammary; 3. Thyrocervical; 4. Costocervical; 5. Descending or Dorsal scapular artery (50% of the time).
Division into four parts
The vertebral artery may be divided into four parts:
The second part runs upward through the foramina in the transverse processes of the C6 to C2 vertebræ, and is surrounded by branches from the inferior cervical sympathetic ganglion and by a plexus of veins which unite to form the vertebral vein at the lower part of the neck.
It is situated in front of the trunks of the cervical nerves, and pursues an almost vertical course as far as the transverse process of the axis.
The third part issues from the C2 foramen transversarium on the medial side of the Rectus capitis lateralis. It is further subdivided into the vertical part V3v passing vertically upwards, crossing the C2 root and entering the foramen transversarium of C1, and the horizontal part V3h, curving medially and posteriorly behind the superior articular process of the atlas, the anterior ramus of the first cervical nerve being on its medial side; it then lies in the groove on the upper surface of the posterior arch of the atlas, and enters the vertebral canal by passing beneath the posterior atlantoöccipital membrane.
This part of the artery is covered by the Semispinalis capitis and is contained in the suboccipital triangle—a triangular space bounded by the Rectus capitis posterior major, the Obliquus superior, and the Obliquus inferior.
The fourth part pierces the dura mater and inclines medialward to the front of the medulla oblongata; it is placed between the hypoglossal nerve and the anterior root of the first cervical nerve and beneath the first digitation of the ligamentum denticulatum.
- Albayrak, Ramazan; Degirmenci, B; Acar, M; Haktanir, A; Colbay, M; Yaman, M (2007). "Doppler sonography evaluation of flow velocity and volume of the extracranial internal carotid and vertebral arteries in healthy adults". J Clin Ultrasound 35 (1): 27–33. doi:10.1002/jcu.20301. PMID 17149761.
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- Anatomy photo:28:09-0201 at the SUNY Downstate Medical Center
- MedEd at Loyola Neuro/neurovasc/navigation/vert.htm
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- Vertebral+artery at eMedicine Dictionary
- lesson5 at The Anatomy Lesson by Wesley Norman (Georgetown University) (vertebralcolumnfromleftweb)
- Anatomy diagram: 13048.000-1 at Roche Lexicon - illustrated navigator, Elsevier
- Anatomy diagram: 13048.000-3 at Roche Lexicon - illustrated navigator, Elsevier