Neuro-Anatomy
Lec: 6 Prof Dr. Al-Hubaity
The Interpeduncular Fossa
Is a depression seen at the base of the brain it is bounded by:
a- The optic chiasma supriorly (anteriorly)
b- The optic tract superolaterally on each side.
c- The cruss cerebri of mid brain inferolaterally on each side.
d- The upper border of the pons inferiorly (postriorly).
It is contents are the followings:
1- Median eminence.
2- Tuber cinereum.
3- Infundibulum (pituitary stalk).
4- Mammilary bodies.
5- Posrerior perforated substance.
6- Occulomotor nerve.
1-5 are infacts hypothalamic structures seen at the base of the brain. Thus
contents are hypothalamic structures + occulomotor nerve. Around the
interpeduncular fossa we can see the circle of willis within the
interpeduncular cistern.
At the base of the brain we can see the following cranial nerves:
1- Olfactory nerve runs on the olfactory sulcus.
2- Optic nerve coming from the optic tract.
3- Occulomotor nerve from the region of the mid brain.
4- Trochlear nerve.
5- Trigeminal nerve arises from the region of the pons, just lateral to it,
the pons continues as middle cerebellar peduncle.
6- Abducent nerve.
7- Facial nerve.
8- Vestibulocochlear nerve.
Emerge from the area between lower border of
pons & upper border of the medulla oblongata.
9- Glossupharyngeal nerve.
10- Vagus.
11- Cranial part of accessory nerve.
12- Hypoglossal nerve Emerges from the medulla oblongata
between pyramid & olive of the medulla oblongata
Blood supply of the brain
The brain forms about 2% of total body weight , but it receives about
10% of the cardiac output as it is the most actively metabolize structure in
the body and consist with stand poor perfusion or cut of its blood supply
for more than 20-30 seconds , and if lasts for a minute there will be a loss
of consciousness, with permenant damage to the part of brain supplies by
that specific artery which is occluded leading to cerebro vascular accident
(C.V.A) or infraction of the brain (stroke).
The brain receives its blood supply from 2 internal carotid arteries and 2
vertebral arteries.
The Vertebral artery
Is a branch of the first part of the subclavian artery at the root of the neck,
passes via foramina transversaria of the successive cervical vertebra C6
till atlas , then it appears in the suboccipital triangle and finally pierce the
dura and arachnoid mater just below the foramen magnum.
It ascends in the subarachnoid space on the antero lateral aspect of the
M.O close to the rootless of hypoglossal nerve and 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 scull are:
Emerge from the medulla oblongata
between the olive & inferior cerebellar
peduncle.
1- Posterior spinal artery, it descends down ward via foramen
magnum as 2 branches, one infront and one behind the dorsal root
of the spinal nerves.
2- Anterior spinal artery, it’s a single artery forms by a contribution
from both right & left vertebral arteries. It descend down word via
foramen magnum in the anterior median fissure of the spinal cord .
It supplies the medial part of the medulla and the anterior 2\3 of the
spinal cord.
3- Medullary branches to supple the M.O.
4- Posterior inferior cerebellar artery, runs backward on the side of
m.o among the rootless of the 9
th
& 10
th
cranial nerves and then
continues on the posterior part of the inferior surface of the
cerebellum. It supplies:
a. Lateral part of M.O.
b. Inferior surface of cerebellum.
c. Choroid plexus of the 4
th
ventricle.
i.e it gives a choroidal branch.
Basilar Artery
Runs on the basilar sulcus on the front of the pons. Here lies on the
basilar part of the occipital bone and the dorsum sellae of the sphenoid
bone. It ends by dividing in to the 2 posterior cerebral arteries
Branches:
1- Pontine branches to supply the pons.
2- Labyrinthine artery goes to internal acoustic meatus with the 7
th
&
8
th
cranial nerves.
3- Anterior inferior cerebellar supplies the anterior part of the inferior
surface of the cerebellum.
4- Superior cerebellar artery from the upper part of the basilar artery,
runs backward to supply the superior surface of the cerebellum.
5- Posterior cerebral artery from the terminal part of basilar artery,
curves around the mid brain (is separated from superior cerebellar
artery by 3
rd
& 4
th
cranial nerves). It reaches medial surface of
occipital lobe where it lies on calcarine sulcus , it gives:
a. Medial central branches pierce the posterior perforated substance
to reach the thalamus.
b. Lateral central branches to supply the cerebral peduncle of mid
brain.
c. Posterior choroidal branch supplies choroid plexus of 3
rd
and
lateral ventricles.
d. Cortical branches to supply the whole occipital lobe and infero
lateral surface of the temporal lobe.
Internal carotid artery
One of the 2 branches 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 foramen
lacerum to run on the carotid groove (on the side of sella turcica) inside
the carvenous sinus , as it leaves the carvenous 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 and
optic tract and passes posteriorly to join the posterior cerebral
artery.
2- Anterior choroidal artery, it passes posterolaterally close to the
optic tract to enter the choroid plexus in the inferior horn of the
lateral ventricle.
3- Anterior cerebral artery , runs anteromedially above the optic
chiasma and runs upward to enter the longitudinal cerebral fissure
from below , here its 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 parieto-
occipital sulcus it gives:
a) Central branches pierce the anterior perforated substance as it
starts.
b) Cortical branches (callosal & callosomarginal branches) to
supply the cortex of the medial medial surface of the cerebral
hemisphere.
4- The internal carotid artery continuous 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:
a) Central branches (striate arteries) pierce the anterior perforated
substance.
b) Cortical branches to supply the lateral surface of the 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 limp and
perineum, also supplies the area of brain responsible for receiving
sensations from opposite half of body except lower limp and
peritoneum. 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 and sensation
of opposite lower limp and half of the peritoneum including
sphincters.
3- Posterior cerebral artery supplies the visual area in the occipital
lobe
Circle of Willis
Inside region of interpeduncular fossa between some branches of I.C.A
and 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.