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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: abcd- The optic chiasma supriorly (anteriorly) The optic tract superolaterally on each side. The cruss cerebri of mid brain inferolaterally on each side. The upper border of the pons inferiorly (postriorly). It is contents are the followings: 123456- Median eminence. Tuber cinereum. Infundibulum (pituitary stalk). Mammilary bodies. Posrerior perforated substance. 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: 12345- Olfactory nerve runs on the olfactory sulcus. Optic nerve coming from the optic tract. Occulomotor nerve from the region of the mid brain. Trochlear nerve. 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. Emerge from the medulla oblongata between the olive & inferior cerebellar peduncle. 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: 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 9th & 10th 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 4th 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 & 8th 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 3rd & 4th 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 3rd 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 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 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 parietooccipital 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: 123456- 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.