الاحد 17/11/2013 أ.د.عبد الجبار الحبيطي Neuro Anatomy الاحد 17/11/2013 أ.د.عبد الجبار الحبيطي

Topography of the brain The parts of the brain are: - Fore brain: - including the cerebrum (2 hemispheres) & Diencephalon (thalamus & hypothalamus). Mid brain: - traverses the tentorial notch & connecting fore brain with hind brain. Hind brain: - occupying the posterior cranial fosse & includes, the Pons, Medulla oblongata (M.O) & Cerebellum.

If we remove the fore brain & cerebellum, the remaining parts of the brain are known as the brain stem which includes: - The mid brain. The Pons. The medulla oblongata. The three parts of the brain stem are connected to the cerebellum by three pairs of cerebellar peduncles as follows: - Mid brain is connected to the cerebellum by superior cerebellar peduncles. Pons is connected to the cerebellum by the middle cerebellar peduncles. Medulla oblongata is connected to cerebellum by the inferior cerebellar peduncles.

The cerebrum - consist of two hemispheres separated from each other by the median longitudinal cerebral fissure (which contains the falx cerebri), at the bottom of the fissure, the two hemisphere are connected together by what is called the corpus callosum (a kind of commissural fibers), each hemisphere consist of four lobes: - frontal, parietal, temporal & occipital, with three poles: - a frontal, temporal & occipital poles. Each hemisphere extends from the frontal bone anteriorly as far as the internal occipital protuberance posteriorly. Where the occipital lobe is separated from cerebellum by the tentorium cerebelli.

Each hemisphere consists of an outer layer of gray mater (cortex) which is thrown into sulci & gyri to increase the surface area of the cerebrum & an inner white mater ( medulla) which contains nerve fibers (axons & dendrites) arranged as fibers of different kinds, namely associated commissural & projecting fibers with supporting element of neuralgia. Inside the medulla we can see scattered small masses of gray mater dispersed as island inside the white mater known as basal ganglia (or nuclei). In addition each cerebral hemisphere has its own cavity called as lateral ventricle with its four parts; anterior horn (for the frontal lobe), body (for parietal lobe), posterior horn (for occipital lobe) & inferior horn (for temporal lobe). The cortex (gray mater) contains the bodies of neurons (nerve cells) & the supporting element of neuroglia.

The Diencephalon Is the other part of fore brain, it is hidden from view (as it is located inferomedial to the two hemisphere), where it joins & is continuous with inferomedial part of the two hemispheres. The only part of the Diencephalon can be seen is the inferior surface of the hypothalamus at the base of the brain. The Diencephalon consists of two halves, one on each side of the third ventricle & both halves are connected together across the cavity by what is called interthalamic connecter. Each half consists of a supero-dorsal part known as thalamus (an important sensory station) & an infero-ventral part called hypothalamus.

The Thalamus is an egg shaped mass of grey mater on each side of the third ventricles with a pointed anterior end (related to interventricular foramen) & broad posterior part known as pulvinar which hides the superior colliculus of the mid brain, the medial surface of the thalamus is related to the cavity of the third ventricle, while the lateral surface is related to the internal capsule (which separates it from the basal ganglion).

Note: - the thalamus contains four geniculate bodies on its dorsal surface, two lateral geniculate bodies (superiorly) being connected to the superior colliculus of the mid brain by a brachium & forming part of the visual pathway. The two medial geniculate bodies are connected to the inferior colliculus of mid brain via a brachium & forms part of the auditory pathway.

The Hypothalamus is related to the cavity of the third ventricle internally & to the internal capsule externally. The hypothalamus is connected to the pituitary gland by infundibulum (pituitary stalk) & in this way the hypothalamus influence the activity & function of the pituitary gland.

The hypothalamus is an important part for the following activity: - Influence the activity of the autonomic nervous system. Control the endocrine glands via its effect on the pituitary. Control the internal homeostasis of the body through I & II. Contains the sleeping center. Contains the sexual center. Thirsty & satiety center.

The Interpeduncular Fossa Is a depression seen at the base of the brain, it is bounded by: - The optic chiasma superiorly (anteriorly). The optic tract supero laterally on each side. The cruss cerebri of mid brain infero laterally on each side. The upper border of the pons inferiorly (posteriorly).

Its contents are the followings: - Median eminence. Tuber cinereum. Infundibulum (pituitary stalk). Mammilary bodies. Posterior perforated substance. Occulomotor nerve. 1-5 are in facts 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: - Olfactory nerve runs on the olfactory sulcus. Optic nerve coming from the optic canal. Occulomotor nerve from the region of the mid brain. Trochlear nerve from the region of the mid brain. Trigeminal nerve arises from the region of the pons, just lateral to it, the pons continues as middle cerebellar peduncle. Abducent nerve emerges from the area between lower border of pons & upper border of the medulla oblongata.

7- Facial nerve emerges from the area between lower border of pons & upper border of the medulla oblongata. 8- Vestibulocochlear nerve emerges from the area between lower border of pons & upper border of the medulla 9- Glossopharyngeal nerve emerges from the medulla oblongata between the olive & inferior cerebellar peduncle. 10- Vagus nerve emerges from the medulla oblongata between the olive & inferior cerebellar peduncle. 11- Cranial part of accessory nerve emerges from the medulla 12- Hypoglossal nerve emerges from the medulla oblongata between pyramid & olive of the medulla oblongata.