13 Cerebral Vasculature

STUDYAIMS

At the end of your study, you should be able to:

State the main arteries that supplythe brain

Describe the course of the vertebral artery

Identifythe arteries contributing to the circle of Willis

Identifythe regions that each of the cerebral arteries supplies

Describe the venous drainage of the brain

Identifythe branches of the external carotid arteryand structures supplied

Describe the division of the subclavian arterybyscalene anterior and the branches given off byeach part

Understand the organization and major vessels of the venous drainage of the head and neck

Understand the principles and organization of the lymphatic drainage of the face and head and neck

Understand the principles and organization of the lymphatic drainage of the neck

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GUIDE

Head and Neck: Cerebral Vasculature

Vascular Supply to the Brain

[Plate 136, Arteries to Brain: Schema]

Arterial Supply

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Internal carotid arteries

Arise from common carotid arteries in neck

Begin at upper border of thyroid cartilage

Have no branches to face or neck

Enter carotid canals in temporal bone, then pass anteriorlyand medially

Run through carotid sinuses in grooves on side of bodyof sphenoid

Terminal branches

Anterior cerebral artery

Middle cerebral artery

Contribute to circle of Willis

United to posterior cerebral arterybyposterior communicating branches

Complete arterial circle around interpeduncular fossa

Provide anterior circulation of brain

Vertebral arteries

First branches of subclavian arteries

Ascend in foramina transversaria of first sixcervical vertebrae

Provide vascular supplyto cervical spinal cord and neck

Pierce dura and enter cranium via foramen magnum

Unite as at caudal end of pons to form basilar artery

Ascends on clivus

Terminates bydividing into two posterior cerebral arteries

Contribute to circle of Willis

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Posterior cerebral arteries unite with anterior cerebral arteries via posterior communicating arteries

Provide posterior circular of brain Cerebral arteries

Each supplies a region of the brain

Anterior cerebral artery

Medial and upper lateral surfaces of cerebral hemisphere

Frontal pole

Middle cerebral artery

Lower and lateral cerebral hemisphere

Temporal pole

Posterior cerebral artery

Inferior surface of cerebral hemisphere

Occipital pole Cerebral arterial circle (circle of Willis)

Lies in subarachnoid space

Important anastomosis at base of brain

Formed by

Anterior communicating arteries

Anterior cerebral arteries

Internal carotid arteries

Posterior communicating arteries

Posterior cerebral arteries

Components supplybrain via manysmall branches

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[Plate 141, Arteries of Posterior Cranial Fossa]

Venous Drainage

Dural venous sinuses

Drain venous blood from superficial and deep veins of the brain

Sinuses drain to internal jugular vein via jugular foramen

Veins on superior and lateral surfaces of brain drain to superior sagittal sinus

Basal veins run laterallyand dorsallyaround cerebral peduncle to end in great vein of Galen, which drains to straight sinus Veins on posterior and inferior surfaces of brain, superior cerebellar veins, and transverse sinuses drain to several sinuses

Straight

Transverse Superior petrosal

Vascular Supply to Scalp, Face, and Neck

Arterial Supply

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Common carotid artery

Branch of aortic arch on left

Branch of brachiocephalic arteryon right

Ascends neck in carotid sheath, beneath anterior border sternocleidomastoid

Bifurcates into internal and external carotid arteries at level thyroid cartilage

Internal carotid arteryhas no branches in the neck

External carotid artery

Begins in upper border thyroid cartilage

Mainlysupplies the face and structures external to the skull, with some branches to the neck

Branches

Ascending pharyngeal

a.Ascends on pharynx

b.Send branches to pharynx, prevertebral muscles, middle ear, and cranial meninges

Superior thyroid

a. Supplies thyroid gland, infrahyoid muscles, and sternocleidomastoid muscle

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b. Gives rise to superior laryngeal arterysupplying larynx Lingual

a.Passes deep to hypoglossal nerve, stylohyoid muscle, and posterior bellyof digastric

b.Disappears beneath hyoglossus muscle and becomes deep lingual and sublingual arteries

Facial

a.Branches to tonsil, palate, and submandibular gland

b.Hooks around middle of mandible and enters face

Occipital

a.Passes deep to posterior bellyof the digastric

b.Grooves base of skull

c.Supplies posterior scalp

Posterior auricular

a.Passes posteriorlybetween external acoustic meatus and mastoid process

b.Supplies muscles of region, parotid gland, facial nerve, auricle, and scalp

Maxillary

a.Larger of two terminal branches

b.Branches supplyexternal acoustic meatus, tympanic membrane, dura mater and calvaria, mandible, gingivae and teeth, temporal pterygoid, masseter, and buccinator muscles

Superficial temporal

a.Smaller terminal branch

b.Supplies temporal region of scalp

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Subclavian artery

Branch of aortic arch on the left

From brachiocephalic trunk on the right

Enters neck between anterior and posterior scalene muscles

Supplies upper limbs, neck and brain

Divided for descriptive purposes into 3 parts, in relation to the anterior scalene muscle

First part

a.Medial to the anterior scalene

b.Has three branches

Second part

a.Posterior to the anterior scalene

b.Has one branch

Third part

a.Lateral to anterior scalene

b.Has one branch

Venous drainage

Superficial veins

External jugular vein (EJV)

Drains most of scalp and side of face

Formed at angle of mandible byunion of retromandibular vein with posterior auricular vein

Enters posterior triangle and pierces fascia of its roof

Descends to terminate in subclavian vein

Receives

a.Transverse cervical vein

b.Suprascapular vein

c.Anterior jugular vein

Anterior jugular vein

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Descends deep to investing fascia

Posterior to sternocleidomastoid (SCM), drains to EJVor subclavian vein

Commonlyunites with anterior jugular on opposite side via a jugular venous arch

Deep veins

Internal jugular vein (IJV)

Most veins in anterior neck are tributaries of IJV

Drains blood from brain, anterior face, cervical viscera, and deep muscles of neck

Begins as dilation of superior bulb just below jugular foramen

Runs inferiorlyin carotid sheath

Inferior end deep to gap between two heads of SCMmuscle

Joins subclavian vein to form brachiocephalic vein

Subclavian vein

Major vein draining upper limb

Passes anterior to anterior scalene muscle

Unites at medial border of muscle with IJVto form brachiocephalic vein

Tributaries of subclavian and IJVtravel with arteries of same name

Lymphatic Drainage

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Drainage of face and head

Superficial lymphatic vessels accompanyveins

Deep lymphatic vessels accompanyarteries

Lymphatic drainage of face

Drainage from lateral face to parotid nodes

Drainage from upper lip and lateral lower lateral lip to submandibular nodes

Drainage from chin and central lower lip to submental nodes

All drain to parotid, mastoid, or superficial cervical nodes

These drain to deep cervical nodes

Drainage of the neck

Superficial drainage to superficial cervical nodes

Located along course of EJV

Also receive drainage from nodes of face and head

Superficial cervical nodes drain to deep cervical nodes

Deep cervical nodes

Lie along course of IJV, transverse cervical artery, and accessorynerve

Include

Prelaryngeal nodes

Pretracheal nodes

Paratracheal nodes

Retropharyngeal nodes

Drain to jugular lymphatic trunk

Jugular lymphatic trunks

On left

Joins thoracic duct on left

Thoracic duct enters junction of IJVand subclavian vein

On right

Empties directlyinto IJVor brachiocephalic vein

Or forms short right lymphatic duct which enters either of these vessels

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[Plate 144, Subependymal Veins of Brain]

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