1. الاربعاء 20/11/2013 LEC.4 أ.د.عبد الجبار الحبيطي
NEURO ANATOMY
الاربعاء /11/2013
LEC.4
أ.د.عبد الجبار الحبيطي

2. 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 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.

3. 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

4. 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: -
Lateral part of M.O.
Inferior surface of cerebellum.
Choroid plexus of the 4th ventricle (i.e. it gives a choroidal branch).

5. 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: -
Pontiue branches to supply the pons.
Labyrinthine artery goes to internal acoustic meatus with the 7th & 8th cranial nerves.
Anterior inferior cerebellar supplies the anterior part of the inferior surface of the cerebellum.
Superior cerebellar artery from the upper part of the basilar artery, runs backward to supply the superior surface of the cerebellum.
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).

6. It reaches medial surface of occipital lobe where it lies on calcarine sulcus, it gives: -
Medial central branches pierce the posterior perforated substance to reach the thalamus.
Lateral central branches to supply the cerebral peduncle of mid brain.
Posterior choroidal branch supplies choroid plexus of 3rd & lateral ventricles.
Cortical branches to supply the whole occipital lobe & inferior lateral surface of the temporal lobe.

7. 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).

8. The I.C.A reaches near the anterior clinoid process as cerebral portion of the artery where it will give: -
Posterior communicating artery: - It supplies the crus cerebri & optic tract & passes posteriorly to join the posterior cerebral artery.
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.
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 parieto-occipital sulcus it gives: -
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.

9. 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: -
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.

10. 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.
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.
Posterior cerebral artery supplies the visual area in the occipital lobe.

11. 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:-
Anterior communicating.
Anterior cerebral of both sides.
The internal carotid artery on each side.
The posterior communicating artery on each side.
Posterior cerebral artery on each side.
Terminal part of basilar artery.

12. 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.

13. The cerebral peduncle is divided into crus cerebri and tegmentum by the substantia nigra.
The crus contains the following descending tracks: -
Cortico-spinal fibers: - occupy the middle 3/5th of the crus cerebri.
Cortico-nuclear fibers: - situated medially to the Cortico-spinal.
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 Cortico-ponto-cerebellar pathway from cerebral cortex to cerebellar cortex).

14. 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

15. 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.

16. 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 extra-ocular 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 .
Nucleus of the trochlear nerve: - in the lower part of midbrain at the level of inf. Colliculus.
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 Fibers or tracts
Rubro-thalamic