Core: common carotid, external carotid, internal carotid, vertebral (and its subclavian origin)

The arch of the aorta gives off the braciocephalic artery, the left common carotid artery and the left subclavian artery.
The braciocephalic artery branches into the right subclavian and right common carotid.
The common carotids divide into external and internal carotid arteries.
The vertebral arteries are branches of the subclavian arteries.
The internal carotid arteries and vertebral arteries are the four main arteries supplying the brain with blood.
These form an internal carotid system and a vertebrobasilar system, respectively, with the former system supplying the anterior and middle parts of the brain, and the latter supplying posterior regions
The internal carotids enter the skull through the carotid canal and form the internal carotid system, which supplies anterior and middle parts of the brain. 80% of blood supply.
The vertebral arteries enter the skull through the foramen magnum and join to form the basilar artery and vertebro-basilar system supplying posterior parts of the brain. 20% of blood supply.

Core: circle of Willis

Extension: arterial anastamoses

These two systems are joined by communicating arteries, forming a large anastomosis at the base of the brain called the circle of Willis.
The circle of Willis is an important protective feature, as blood supply to a particular region can be maintained, at least to a certain extent, by flow through other vessels if one becomes occluded.
Blood flow through these anastomoses is limited, however, such that occlusion of an artery can lead to serious ischaemia.

The vertebro-basilar system

The vertebral artery and its branches

The vertebral arteries run in the transverse foramina of the upper six cervical vertebrae then pass through the foramen magnum and run over the ventral surface of the medulla.
They give off a number of branches:

Core: posterior inferior cerebellar

The posterior inferior cerebellar arteries are the largest branches of the vertebral artery.
They branch off at the level of the caudal end of the medulla, running dorsally and laterally around the brainstem, supplying the lateral parts of the medulla.
They have a tortuous course amongst the glossopharyngeal, hypoglossal and vagus nerve rootlets.
They then run towards the ventral, caudal region of the cerebellum, which they supply.
They also have a branch supplying the choroid plexus of the fourth ventricle.

Core: posterior spinal

The posterior spinal arteries may branch directly from the vertebral artery but more commonly branch from the posterior inferior cerebellar arteries.
They run caudally, through the foramen magnum and over the posterior surface of the spinal cord.

Core: anterior spinal

The anterior spinal arteries branch off just before the formation of the basilar artery and run caudally and medially, uniting in the midline to form a single artery.
This runs in the anterior medial fissure of the medulla, giving off fine branches that supply some regions of the medulla.
It then exits through the foramen magnum and runs caudally over the anterior surface of the spinal cord, which it supplies.

Core: reinforcement of spinal supply – artery of Adamkiewicz

It typically arises from a left posterior intercostal artery which branches from the aorta and supplies the lower two thirs of the spinal cord via the anterior spinal artery

The basilar artery and its branches

Core: basilar

At the inferior end of the pons the vertebral arteries join to form the basilar artery, which runs rostrally in the basilar groove of the pons.

Extension: anterior inferior cerebellar artery

Extension: the anterior inferior cerebellar artery branches from the caudal part of the basilar artery.
It runs laterally and posteriorly to the antero-lateral parts of the inferior aspect of the cerebellum and anastomoses with the posterior inferior cerebellar artery.

Core: pontine

The pontine arteries are a number of small branches that enter and supply the pons.
Extension: the labyrynthine artery is a small branch that enters the internal auditory meatus with the facial and vestibulocochlear nerves, providing the supply to the inner ear.
If occluded, vertigo and ipsilateral deafness can occur.
The superior cerebellar artery branches close to the termination of the basilar artery.
It winds laterally over the cerebral peduncle (roughly corresponds to the mesencephalon) and runs over the superior surface of the cerebellum.

Core: posterior cerebral

The occulomotor nerve and free edge of the tentorium cerebelli separate it from the posterior cerebral artery.
The terminal branches of the basilar artery are the posterior cerebral arteries, which can be seen at the rostral border of the pons.
They run laterally around the cerebral peduncles to the posterior surface of the cerebrum, supplying parts of the occipital and temporal cortex, including the visual cortex.
There are therefore often losses of vision if this artery is occluded.
Close to the branch point of the posterior cerebral arteries, they give off the posterior communicating arteries, which link them to the internal carotid arteries in the circle of Willis.

Core: posterior perforating

Many perforating arteries branch from the posterior cerebral and posterior communicating arteries.
These enter deeper structures of the brain between the cerebral peduncles in a region known as the interpeduncular fossa or posterior perforated substance.
These posterior perforating arteries supply mainly the medulla and thalamus.

The internal carotid system

The internal carotid artery and its branches

The internal carotid artery passes through the carotid canal of the temporal bone then emerges into the brain via Foraemn lacerum in the cavernous sinus before emerging in the sub-arachnoid space close to the lateral cerebral sulcus.
If this vessel is cut, it can be seen lateral to the optic chiasm.
Occlusion of the internal carotid artery usually leads to similar symptoms to occlusion of the middle cerebral artery, with additional loss of sight on the ipsilateral side.

Core: ophthalmic

The ophthalmic artery is a branch given off as the internal carotid emerges from the cavernous sinus.
It enters the orbit through the optic canal, which is caudal and lateral to the optic nerve.
It supplies the eye and other structures of the orbit and has terminal branches to the frontal area of the scalp, the ethmoid and frontal sinuses and the dorsum of the nose.
It gives off the posterior communicating arteries, joining to the posterior cerebral arteries in the circle of Willis.

Extension: choroidal arteries

The choroidal artery is a small branch that arises close to the terminal bifurcation of the internal carotid.

It runs posteriorly to the choriod plexus of the lateral ventricles, supplying it as well as some surrounding structures, such as the crus cerebri, optic tract and internal capsule.
The terminal bifurcation of the carotid arteries gives the middle and anterior cerebral arteries.

The middle cerebral artery and its branches

Core: middle cerebral

The middle cerebral artery is larger than the anterior cerebral artery and runs laterally to the region of the lateral sulcus, where it gives off many branches, supplying most of the lateral surface of the cerebral hemispheres.
Temporal lobe and basal ganglai
This includes most of the motor regions of the cortex, not including the ‘leg area’.

Core: anterior perforating

It also gives off a number of small perforating arteries close to its origin, forming the anterior perforated substance lateral to the optic chiasm.
These anterior perforating arteries supply the deep structures of the anterior part of the forebrain.

Core: striate

Some of the deep arteries branching from the middle/anterior cerebral artery are known as the striate arteries.
When occluded it leads to dramatic loss of motor and somatosensory function on the contralateral side, as they supply most of the pre and post-central gyri.
Aphasia can also occur if the left hemisphere is affected or anosognosia if the right hemisphere is affected.

The anterior cerebral artery and its branches

Core: anterior cerebral

The anterior cerebral artery runs rostrally and medial to the great longitudinal fissure, where it gives off the anterior communicating artery connecting it to the other anterior cerebral artery in the circle of Willis.
The anterior cerebral artery runs along the outline of the corpus callosum and anastomoses posteriorly with branches of the posterior cerebral artery.
It supplies the medial surface of the cerebral hemisphere (the frontal and parietal lobes).
If occluded, loss of supply to this region leads to inability to correctly identify objects, apathy and personality changes.
It also supplies a small region of the lateral surface corresponding to the ‘leg motor area’ (the paracentral lobule).
Occlusion can therefore leads to some impeded motor and somatosensory function in the leg and foot on the contralateral side.
It also gives off branches near its origin which enter deep parts of the hemisphere as part of the anterior perforated substance.

The external carotid artery and its branches

This is the major artery to the head and neck, supplying regions outside of the skull.
Its terminal branches are the maxillary and superficial temporal arteries.

Core: middle meningeal

The maxillary artery gives off a large branch supplying the dura mater, known as the middle meningeal artery.
This artery is of clinical relevance because it is the major cause of an...

#14104 - Blood Supply To The Brain - Neuroscience 1

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