Download Neuro Anatomy Lec.4 أ.د.عبد الجبار الحبيطي Blood supply of the

Neuro Anatomy
‫عبد اجلبار احلبيطي‬.‫د‬.‫أ‬
Lec.4
Blood supply of the brain: The brain form about 2% of total body weight, but it receive
about 10% of the cardiac output as it is the most actively
metabolic structure in the body & can’t with stand poor
perfusion or cut of its blood supply for more than 20-30
seconds, & if last for a minute there will be loss of
consciousness with permanent damage to the part of the brain
supplies by that specific artery which is occluded leading to
cerebro vascular accident (C.V.A) or infarction of the brain
(stroke). The brain receives its blood supply from 2 internal
carotid arteries & 2 vertebral arteries.
The vertebral artery: Is a branch of the first part of subclavian artery at the root of
the neck, passes via foramina transversaria of the successive
cervical vertebral C6- till atlas, then it appear in the suboccipital
triangle & finally pierces the dura & arachnoid mater just below
the foramen magnum.
It ascends in the subarachnoid space on the anterolateral
aspect of the M.O close to the rootlets of hypoglossal nerve &
finally unites with its fellow of the opposite side at the lower
border of the pons to form the basilar artery, its branches
inside the skull are: I.
Posterior spinal artery: - it descends down wards via
foramen magnum as 2 branches, one in front & one
behind the dorsal root of the spinal nerves.
II.
Anterior spinal artery: - it’s a single artery forms by a
contribution from both right & left vertebral arteries. It
descends down wards via foramen magnum in the
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anterior median fissure of the spinal cord. It supplies the
medial part of the medulla & the anterior 2/3 of the
spinal cord.
III.
Medullary branches to supply M.O.
IV.
Posterior inferior cerebellar artery: - runs back wards on
the side of M.O. among the rootlets of the 9th & 10th
cranial nerves & then continues on the posterior part of
the inferior surface of the cerebellum. It supplies: i.
Lateral part of M.O.
ii.
Inferior surface of cerebellum.
iii.
Choroid plexus of the 4th ventricle (i.e. it gives a
choroidal branch).
Basilar artery
Runs on the basilar sulcus on the front of the pons, here it lies
on the basilar part of the occipital bone & the dorsum sellae of
the sphenoid bone. It ends by dividing into the 2 posterior
cerebral arteries.
Branches: I.
Pontiue branches to supply the pons.
II.
Labyrinthine artery goes to internal acoustic meatus with
the 7th & 8th cranial nerves.
III.
Anterior inferior cerebellar supplies the anterior part of
the inferior surface of the cerebellum.
IV.
Superior cerebellar artery from the upper part of the
basilar artery, runs backward to supply the superior
surface of the cerebellum.
V.
Posterior cerebral artery from the terminal part of basilar
artery, curves around the mid brain (is separated from
superior cerebellar artery by 3rd & 4th crainal Ns).
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It reaches medial surface of occipital lobe where it lies on
calcarine sulcus, it gives: i- Medial central branches pierce the posterior perforated
substance to reach the thalamus.
ii- Lateral central branches to supply the cerebral peduncle
of mid brain.
iii- Posterior choroidal branch supplies choroid plexus of 3rd
& lateral ventricles.
iv- Cortical branches to supply the whole occipital lobe &
inferior lateral surface of the temporal lobe.
Internal carotid artery: One of the 2 branch of common carotid artery arises in the
neck and ascends to reach the opening of the carotid canal at
the base of the skull, where it enters the canal (in the petrous
bone here it gives carotico-tympanic artery) surrounded by
perivascular internal carotid plexus from superior cervical
sympathetic ganglion in the neck region. The I.C.A. leaves
carotid canal to become as intracranial part bridges over
foremen lacerum to run on the carotid groove (on the side of
sella turcica) inside the cavernous sinus, as it leaves the
cavernous sinus it gives an ophthalmic branch (goes to optic
canal).
The I.C.A reaches near the anterior clinoid process as cerebral
portion of the artery where it will give: I.
Posterior communicating artery: - It supplies the crus
cerebri & optic tract & passes posteriorly to join the
posterior cerebral artery.
II.
Anterior choroidal artery: - It passes postero laterally
close to the optic tract to enter the choroid plexus in the
inferior horn of the lateral ventricle.
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III.
Anterior cerebral artery: - Runs antero medially above the
optic chiasma & runs upward to enter the longitudinal
cerebral fissure from below, here it is connected with its
fellow of the opposite side by anterior communicating
artery (from both anterior cerebral). In the fissure the
artery will run on the corpus callosus to supply the medial
surface of the cerebral hemisphere as far as the parietooccipital sulcus it gives: i. Central branches pierce the anterior perforated substance
as it starts.
ii. Cortical branches (callosal & calloso marginal branches) to
supply the cortex of the medial surface of the cerebral
hemisphere.
IV.
Then internal carotid artery continues as middle cerebral
artery, that runs on the lateral sulcus to supply the lateral
surface of the cerebral hemisphere as far as the parietooccipital sulcus it gives off: i. Central branches (striate arteries) pierce the anterior
perforated substance.
ii. Cortical branch to supply the lateral surface of cerebral
hemisphere except part of lateral aspect of occipital lobe.
Notes: 1- Middle cerebral artery supplies the area responsible for
controlling movement of opposite half of body except
lower limb & perineum, also supplies the area of brain
responsible for receiving sensations from opposite half of
body except lower limb & perineum. It supplies also
motor speech area of the brain.
2- Anterior cerebral artery supplies an area known as
paracentral lobule which is responsible for voluntary
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movement & sensations of opposite lower limb and half
of the perineum including sphincters.
3- Posterior cerebral artery supplies the visual area in the
occipital lobe.
Circle of willis: In the region of interpeduncular fossa between some branches
of I.C.A & posterior cerebral arteries of the basilar artery forms
as:1- Anterior communicating.
2- Anterior cerebral of both sides.
3- The internal carotid artery on each side.
4- The posterior communicating artery on each side.
5- Posterior cerebral artery on each side.
6- Terminal part of basilar artery.
The midbrain
It connects the diacephalon above with the medulla oblongata below. It
is divided into two parts by cerebral aqueduct anterior part known as
cerebral peduncle and posterior part known as tectum.
The cerebral peduncle is divided into crus cerebri and tegmentum by the
substantia nigra.
The crus contains the following descending tracks: a) Cortico-spinal fibers: - occupy the middle 3/5th of the crus
cerebri.
b) Cortico-nuclear fibers: - situated medially to the Corticospinal.
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c) Cortico-pontine fibers: - occupy the medial 1/5th and the
lateral 1/5th of the crus according to the site of origin of these
fibers, the fibers coming from the frontal lobe occupy the medial
1/5th, while those coming from the occipital and temporal lobes
occupy the lateral 1/5th of the crus (there will form Corticoponto-cerebellar pathway from cerebral cortex to cerebellar
cortex).
Substantia nigra separates the crus cerebri from the tegmentum & is
an important extrapyramidal centre.
Each crus cerebri has the following relations:  Laterally : on each side
- Trochlear nerve , optic tract (cross the crus from behind
forward )
- Some blood vessels (posterior cerebral , superior
cerebellar arteries and basal vein)
 Medially :
- Posterior perforated substance (pierced by striate or
central branches).
- Occulomotor nerve
The tegmentum: Is continuous below with the tegmental part of the Pons, the part of the
tegmentum of the superior colliculus contains red nucleus (an important
extrapyramidal centre), While at the level of inferior colliculus the
tegmentum receives the decussation of the 2 superior cerebellar
peduncles.
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The nuclei in the midbrain:
i- The nucleus of the occulomotor nerve : at the level of
superior colliculus , it is a motor nucleus supplies 5 of the extraocular muscles , and also contains edinger-westphal nucleus as
a parasympathetic part whose fibers goes to ciliary ganglion to
supply constrictor pupillae muscle and ciliary body .
ii- Nucleus of the trochlear nerve: - in the lower part of
midbrain at the level of inf. Colliculus.
iii- Red nucleus: - in the tegmentum at the level of sup. Colliculus
, it receives afferent from the frontal cortex , corpus striatus and
cerebellum , while it sends efferent as: -
 Rubro-veticular
 Rubro-spinal
 Rubro-thalamic
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