Assalamu alaikom, welcome again! In today's video we'll be going through the blood
supply of different parts of the brain. As for the blood supply of the brain we
will start by mentioning the arterial supply. The arterial supply consists
mainly of: anterior and posterior systems. Let's start with the posterior system,
also known as: vertebrobasilar system. From the subclavian arteries on both
sides they give rise to: right and left vertebral arteries, these arteries will
ascend through passing in the transverse foramina of the cervical vertebra. The
arteries on both sides will enter the skull through: the foramen magnum. Before
both arteries unite, they will give rise to right and left branches located on
the interior side of the medulla. These branches will converge to form anterior
spinal artery, which will descend and run in the anterior median fissure of the
spinal cord. Also from left and right vertebral arteries, the posterior spinal
arteries will travel along the dorsal part of the spinal cord, and they will
travel as two separate arteries. They arise either from the right and left
vertebral arteries, as we mentioned, or they may arise from the posterior
inferior cerebellar artery, which we will be discussing next. After both vertebral
arteries entered through the foramen magnum, each vertebral artery will give
one branch at the lower level of the medulla on both sides, which is: posterior
inferior cerebellar artery. This artery supplies lateral side of the medulla, as
well as, lower level of the cerebellum, and inferior cerebellar peduncle. Then
they will converge at the level of ponto-medullary junction to form: basilar
artery. The basilar artery will give two branches, one on each side, which is:
anterior inferior cerebellar artery. Anterior inferior cerebellar artery will
supply the pons, lateral cerebellar surface, and middle cerebellar peduncle.
Then the basilar artery will give short branches to supply the pons,
these are known as: pontine branches. The basilar artery
then gives rise to: superior cerebellar artery, below the third cranial nerve. The
superior cerebellar artery will supply the midbrain, upper side of the
cerebellum, and superior cerebellar peduncle.
Lastly the terminal branches of the basilar artery are: posterior cerebral
arteries. They arise above the level of the third cranial nerve, and the
posterior cerebral artery will supply part of the midbrain, part of the
thalamus, and the occipital lobe. So if the posterior cerebral artery is
occluded, the patient will have many problems among them which is related to
the occipital lobe: contralateral homonymous hemianopsia with macular
sparing. So if the patient has right posterior cerebral artery occlusion he
or she will lose the left field of vision on both right and left eyes, with
the macula or the center spared. Now let's go to the anterior circulation
responsible of supplying the brain. Starting from internal carotid artery it
will enter the skull and start giving off branches. First we have ophthalmic
artery, which will give rise to: central retinal artery to supply the eyes. Then
we have anterior choroidal artery, and this will supply choroid plexus and the
lateral ventricle and many other areas of the cerebrum. Then we have hypophyseal arteries,
which will form mainly the arterial network around the pituitary gland. Then the internal
carotid artery will bifurcate to give rise to anterior, and middle cerebral
arteries. The middle cerebral artery will go laterally through the lateral sulcus
and supply mainly the lateral hemispheres, except the superior 1 inch
of the parietal and frontal lobes. These two areas are supplied by the anterior
cerebral arteries. The middle cerebral artery also supplies parts of internal
capsule, posterior limb, and the genu, in which corticospinal and corticobulbar
tracts are passing. So if middle cerebral artery got occluded, the patient will
have many problems, most importantly: contralateral hemiplegia or hemiparesis
of the face and upper limbs, contralateral loss of sensation of the
face and upper limbs, he or she will also have aphasia > if the dominant hemisphere
is affected (usually the left one) and due to the presence of Broca's and
Wernicke's areas. On the other hand, if the non-dominant hemisphere is affected,
the patient will have hemi-neglect syndrome. Now let's discuss the anterior
cerebral artery: it goes anteriorly and supplies the medial aspect of each
hemisphere. The medial aspect of the cerebral hemisphere is responsible for
lower extremities. Anterior cerebral artery also supplies area of the brain
responsible of olfactory bulb and tract. So can you expect the complications of
anterior cerebral artery is occluded? You're right! The patient will have
contralateral loss of sensation as well as motor supply of the lower
limbs, and also the patient will have insomnia : which is loss of smell
sensation. Now let's try to form a circuit between these arteries, and
between anterior and posterior systems. So we have anterior communicating artery,
which connects right and left anterior cerebral arteries. One thing to keep in
mind is that anterior communicating artery has the highest chance of
developing aneurysm in Circle of Willis. Now to complete the Circle of Willis, the
posterior communicating arteries on both sides will connect internal carotid
artery with posterior cerebral artery, forming a complete circle called again:
circle of Willis! Lastly to conclude our video, we will mention briefly the venous
drainage of the brain. So we have meningeal veins in the dura mater
responsible of drainage. These veins will eventually drain into one or more of the
valveless sinuses, which are: superior sagittal sinus, then we have inferior
sagittal sinus, and both superior sagittal and inferior sagittal sinuses
are present in falx cerebri. The inferior sagittal sinus will meet with the
great cerebral vein to form: the straight sinus. Then we have the transverse sinus.
The right transverse sinus will receive blood from the superior sagittal sinus,
while the left transverse sinus will receive blood from the straight sinus.
Then the right and left transverse sinuses will continue as right and left
sigmoid sinuses. These two sinuses will descend through the jugular foramena
to be known as: internal jugular vein. Then we have the petrosal sinuses:
superior and inferior, and lastly the cavernous sinus. And this is it for the
blood supply! Hope you enjoyed! Please don't forget to
Like and subscribe our video to get our new videos explanations.
Till the next time!