Download Internal carotid artery

‫‪NEURO ANATOMY‬‬
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‫‪LEC.4‬‬
‫أ‪.‬د‪.‬عبد الجبار الحبيطي‬
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: 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.
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 anterior
median fissure of the spinal cord. It supplies the medial part of
the medulla & the anterior 2/3 of the spinal cord.
Medullary branches to supply M.O.
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: -
1.
2.
3.
4.
I.
II.
III.
Lateral part of M.O.
Inferior surface of cerebellum.
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).
It reaches medial surface of occipital lobe
where it lies on calcarine sulcus, it gives: 1. Medial central branches pierce the posterior
perforated substance to reach the thalamus.
2. Lateral central branches to supply the cerebral
peduncle of mid brain.
3. Posterior choroidal branch supplies choroid
plexus of 3rd & lateral ventricles.
4. 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 caroticotympanic 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: 1. Posterior communicating artery: - It supplies the crus
cerebri & optic tract & passes posteriorly to join the
posterior cerebral artery.
2. 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.
3. 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.
II.
Central branches pierce the anterior perforated substance as it
starts.
Cortical branches (callosal & calloso marginal branches) to supply
the cortex of the medial surface of the cerebral hemisphere.
4- 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 parieto-occipital sulcus it gives off: i.
ii.
Central branches (striate arteries) pierce the anterior
perforated substance.
Cortical branch to supply the lateral surface of cerebral
hemisphere except part of lateral aspect of occipital lobe.
Notes
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
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.
1.
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
Cortico-spinal.
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.
The nuclei in the midbrain
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: i.
 Rubro-veticular
 Rubro-spinal
 Rubro-thalamic
Fibers or tracts