The vertebral arteries are major

arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pu ...

of the neck. Typically, the vertebral arteries originate from the

subclavian arteries In human anatomy, the subclavian arteries are paired major arteries of the upper thorax, below the clavicle. They receive blood from the aortic arch. The left subclavian artery supplies blood to the left arm and the right subclavian artery supplie ...

. Each vessel courses superiorly along each side of the neck, merging within the skull to form the single, midline

basilar artery The basilar artery () is one of the arteries that supplies the brain with oxygen-rich blood. The two vertebral arteries and the basilar artery are known as the vertebral basilar system, which supplies blood to the posterior part of the circle of W ...

. As the supplying component of the ''vertebrobasilar vascular system'', the vertebral arteries supply blood to the upper

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

, brainstem, cerebellum, and posterior part of brain.

Structure

The vertebral arteries usually arise from the posterosuperior aspect of the central subclavian arteries on each side of the body, then enter deep to the transverse process at 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 of each

cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sa ...

. Once they have passed through the transverse foramen of C1 (also known as the

atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...

), the vertebral arteries travel across the posterior arch of C1 and through the

suboccipital triangle The suboccipital triangle is a region of the neck bounded by the following three muscles of the suboccipital group of muscles: * Rectus capitis posterior major - above and medially * Obliquus capitis superior - above and laterally * Obliquus cap ...

before entering the foramen magnum.

Nunziante Ippolito Nunziante Ippolito (Nunciante) was an Italian physician and anatomist. He studied in Naples and worked in one of the most important hospitals of the Reign of Two Sicilies and Europe, the Ospedale degli Incurabili. He worked also at Pellegrini hos ...

, a Neapolitan physician, identified the "angle of Nunziante Ippolito" to find the vertebral artery, between the anterior scalene muscle and the longus colli muscle. Inside the skull, the two vertebral arteries join to form the

at the base of the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

. The

is the main blood supply to the brainstem and connects to the

Circle of Willis The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including huma ...

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 the

anterior spinal arteries In human anatomy, the anterior spinal artery is the artery that supplies the anterior portion of the spinal cord. It arises from branches of the vertebral arteries and courses along the anterior aspect of the spinal cord. It is reinforced by severa ...

The vertebral artery may be divided into four parts: * The first (preforaminal) part runs upward and backward between the

Longus colli The longus colli muscle (Latin for ''long muscle of the neck'') is a muscle of the human body. The longus colli is situated on the anterior surface of the vertebral column, between the atlas and the third thoracic vertebra. It is broad in the mid ...

and the

Scalenus anterior The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the third to the eight cervical spinal nerves (C3-C8). The anterior and m ...

. In front of it are the internal jugular and

vertebral vein The vertebral vein is formed in the suboccipital triangle, from numerous small tributaries which spring from the internal vertebral venous plexuses and issue from the vertebral canal above the posterior arch of the atlas. They unite with small v ...

s, and it is crossed by the

inferior thyroid artery The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and als ...

; the left vertebral is crossed by the

thoracic duct In human anatomy, the thoracic duct is the larger of the two lymph ducts of the lymphatic system. It is also known as the ''left lymphatic duct'', ''alimentary duct'', ''chyliferous duct'', and ''Van Hoorne's canal''. The other duct is the righ ...

also. Behind it are the transverse process of the seventh

, the

sympathetic trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system. Structure The sympathetic trunk lies j ...

and its

inferior cervical ganglion The inferior cervical ganglion is situated between the base of the transverse process of the last cervical vertebra and the neck of the first rib, on the medial side of the costocervical artery. Its form is irregular; it is larger in size than th ...

* The second (foraminal) part runs upward through the transverse foramina of the C6 to C2 vertebrae, 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 (extradural or atlantic) part issues from the C2 foramen transversarium on the medial side of the

Rectus capitis lateralis The rectus capitis lateralis, a short, flat muscle, arises from the upper surface of the transverse process of the atlas, and is inserted into the under surface of the jugular process of the occipital bone. Additional images File:Rectus capitis ...

. 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 The semispinalis muscles are a group of three muscles belonging to the transversospinales. These are the semispinalis capitis, the semispinalis cervicis and the semispinalis thoracis. The semispinalis capitis (''complexus'') is situated at the ...

and is contained in the

—a triangular space bounded by the

Rectus capitis posterior major The rectus capitis posterior major (or rectus capitis posticus major, both being Latin for ''larger posterior straight muscle of the head'') arises by a pointed tendon from the spinous process of the axis, and, becoming broader as it ascends, is in ...

, the

Obliquus superior The superior oblique muscle, or obliquus oculi superior, is a fusiform muscle originating in the upper, medial side of the orbit (i.e. from beside the nose) which abducts, depresses and internally rotates the eye. It is the only extraocular mus ...

, and the Obliquus inferior. The first cervical or

suboccipital nerve The suboccipital nerve (first cervical dorsal ramus) is the dorsal primary ramus of the first cervical nerve (C1). It exits the spinal cord between the skull and the first cervical vertebra, the atlas. It lies within the suboccipital triangle ...

lies between the artery and the posterior arch of the atlas. * The fourth (intradural or intracranial) part pierces the

dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...

and inclines medialward to the front of the medulla oblongata; it is placed between the

hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated by ...

and the anterior root of the first cervical nerve and beneath the first digitation of the ligamentum denticulatum. At the lower border of the

it unites with the vessel of the opposite side to form the

Triangle

Triangle of the vertebral artery is a region within the root of the neck and has following boundaries: * Medial border of

anterior scalene muscle The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the anterior scalene, middle scalene, and posterior scalene. They are innervated by the third to the eight cervical spinal nerves (C3-C8). The anterior and ...

(lateral) * Lateral border of longus colli muscle (medial) * Carotid tubercle (apex) * First part of subclavian artery (base) The vertebral artery runs from base to apex (prior to entering the transverse foramen of 6th cervical vertebra). The carotid tubercle separates the vertebral artery which passes directly behind it from the common carotid artery which lies directly in front of it. The ideal site for palpating the carotid pulse is to gently press the

common carotid artery In anatomy, the left and right common carotid arteries (carotids) (Entry "carotid"
in
hypoplasia of one side, with studies estimating a prevalence of unilateral vertebral artery hypoplasia between 2% to 25%. In 3-15% of the population, a bony bridge called the

arcuate foramen In human anatomy, arcuate foramen, also known as ponticulus posticus (Latin for "little posterior bridge") or Kimmerle's anomaly, refers to a bony bridge on the atlas (C1 vertebra) that covers the groove for the vertebral artery. It is a common a ...

covers the groove for the vertebral artery on vertebra C1. Rarely, the vertebral arteries enter the subarachnoid space at C1-C2 (3%) or C2-C3 (only three cases have been reported) vertebral levels instead of the atlanto-occipital level. The portion of vertebral arteries located within the skull (intracranial) have diameters of 3.17 mm. The intracranial length for the left vertebral artery (32.4 mm) is longer than the right (31.5 mm). The angle where vertebral arteries meet the

(vertebrobasilar junction), is 46 degrees.

Function

As the supplying component of the ''vertebrobasilar vascular system'', the vertebral arteries supply blood to the upper

, brainstem, cerebellum, and posterior part of brain.

Clinical significance

As the supplying component of the ''vertebrobasilar vascular system'', the vertebral arteries supply blood to the upper

, brainstem, cerebellum, and posterior part of brain. A stroke of the arteries may result in a posterior circulation stroke.

Chiropractic Chiropractic is a form of alternative medicine concerned with the diagnosis, treatment and prevention of mechanical disorders of the musculoskeletal system, especially of the spine. It has esoteric origins and is based on several pseudosci ...

manipulation of the neck has the potential to cause a vertebral arterial dissection.ucsf.edu/news/2003/05/97065/chiropractic-treatment-neck-can-be-risk-factor-stroke

Additional images

File:Sobo 1909 3 548.png, The arteries of the base of the brain (inferior view). File:Circle of Willis en.svg, Diagram of the arterial circulation at the base of the brain. File:Suboccipital triangle dissection.jpg, Relationship of the vertebral artery to the suboccipital muscles.

References

External links

*
Vertebral Artery , neuroangio.org
* * * () * * {{Authority control Arteries of the head and neck