1. EMBRYOLOGY OFNERVOUS SYSTEMDr NAVEEN THOTASVIMS

2. Introduction Formation of neurons and neuroglial cells Neural tube and its sub divisions Spinal cord Medulla oblongata Pons Midbrain Cerebral hemisphere Corpus striatum Cerebral cortex Autonomic nervous system 3. Formation of neurons andneuroglial cells Neural tube first lined by single layerof cells Proliferate to form several layers Matrix layer Mantle layer Marginal layer 4. Contd.. Stages in the formation of a nerve cellare: Apolar neuroblast Bipolar neuroblast Unipolar neuroblast Multipolar neuroblast Axon and dendrites 5. Neuroglial cells are also formed fromgerminal cells of the ependymal layer Glioblasts migrate in to mantle andmarginal layer as medulloblasts They differentiate either intoastroblasts or oligodendroblasts Microglial cells are mesodermal inorigin 6. Myelination of fibers Nerve fibers which remain with in thebrain and spinal cord receives supportfrom and are ensheathed by neuroglialcells Peripheral nerves special sheathcalled the neurolemma derived fromschwann cells Myelin of the CNS derived fromoligodendrocytes 7. Neural tube and itssubdivisions Whole of the nervous system isderived from ectoderm except bloodvessels and neuroglial elements Ectoderm situated on the dorsalaspect of embryonic disc forms theneural plate Neural groove Neural tube Enlarges cranial part and caudaltubular part 8. Contd.. The cavity of the brain shows threedilatations Prosencephalon, mesencephalon,rhombencephalon Prosencephalon Diencephalon Telencephalon Rhombencephalon Metencephalon Myelencephalon 9. Contd.. The relative position is altered bynumber of flexures Cervical flexure Mesencephalic flexure Pontine flexure Telencephalic flexure 10. Neural crest Cells between the neural plate and therest of the ectoderm form primordia ofthe neural crest DRG Sensory ganglia of 5, 7, 9, 10 Neurons and satellite cells of sympatheticganglia Parasymathetic ganglia Schwann cells 11. Contd.. Specific cells adrenal medulla Chromaffin tissue melanoblasts 12. Spinal cord Devolops from caudal cylindrical part ofneural tube Cavity of the tube bounded by thicklateral wall, thin roof and floor Tube subdivides in to three layers matrixlayer, mantle layer and marginal layer Ventral layer of the mantle layer growsfaster than dorsal layer Line seperating the compressed ventralpart from the dorsal part is called sulcuslimtans 13. Contd.. Dorsal or alar lamina Ventral or basal lamina Posteriomedeian fissure Anteriomedian fissure Nerve cells that devolop in mantlezone of the basal lamina becomes theneuron of anterior grey column andfrom the alar lamina the neuron of theposterior grey column 14. Contd.. Dorsal nerve root ganglia are formedby axons of the cells that develop fromneural crest Axons from the post grey columnenter the marginal layer to form theascending tract Descending tracts are formed by theaxons projecting from the brain Grey columns divide the white matterin to anterior, posterior and lateralcolumns 15. POSITIONAL CHANGES OFTHE CORDIn the third month of development the spinal cord extendsthe entire length of the embryo, and spinal nerves passthrough the intervertebral foramina at their level of origin.With increasing age, the vertebral column and duralengthen more rapidly than the neural tube, and the terminalend of the spinal cord gradually shifts to a higher level. At birth, this end is at the level of the third lumbarvertebra. As a result of this disproportionate growth, spinal nerves runobliquely from their segment of origin in the spinal cord tothe corresponding level of the vertebral column. The dura remains attached to the vertebral column at thecoccygeal level. In the adult, the spinal cord terminates at the level of L2 toL3, The dural sac and subarachnoid space extend to S2.Below L2 to L3, a threadlike extension of the pia materforms the filum terminale, which is attached to theperiosteum of the first coccygeal vertebra and which marksthe tract of regression of the spinal cord. Nerve fibers below the terminal end of the cord collectivelyconstitute the cauda equina. 16. Medulla oblongata Myelencephalon Early devolopment simillar to spinalcord sulcus limitans divides in to alarand basal lamina Roof plate becomes greatly widenedresuting which alar plate comesdorsolateral to basal plate Alar plate forms olivary nuclei andcranial nerve nuclei 17. Contd.. 18. Pons Ventral part of metencephalon Contribution alar lamina of themyelencephalon and gives rise topontine nuclei axons arising from themforms MCP Lateral part of alar lamina becomesrhombic lips to form the cerebellum Nuclei arising from basal and alarplate lie in dorsal or tegmental part ofpons 19. Contd.. Ventral part of pons constitutes: Middle cerebellar peduncle Corticospinal, corticobulbar andcorticopontine fibers 20. Mid brain Nuclei of the basal lamina Occulomotor nuclei Trochlear nuclei Edinger Westphal nuclei Alar lamina gives rise to Colliculi Red nucleus Substantia nigra 21. Contd.. Marginal layer ventral part ofmesencephalon invaded by downgrowing fibers of CST, corticobulbarand cortico pontine pathway andforms crus cerebri 22. Cerebellum Devolops from dorsolateral part of alarlamina of the metencephalon Rhombic lips on either side grows andfuses medially to form cerebellum Consists of usual matrix, mantle andmarginal layer Cells of the mantle layer migrating in tomarginal layer forms cortex and thosedont forms dentate, emboliform, fastigialand globose nuclei 23. Contd.. Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle 24. Cerebral hemispheres Median diencephalon and lateraltelencephalon Telancephalon Cerebral cortex and corpus striatum Diencephalon Epithalamus, thalamus and hypothalamus Telencephalic vesicles are smallinitially rapidly grows upwards,forwards and backwards completelycovers the diencephalon 25. Contd.. Cavity of diencephalon form thirdventricle and of telencephalic vesiclesform lateral ventricles Each lateral is at first a small sphericalspace Forward and backward growth elongatesanterioposteriorly Grows downwards and forwards to form thetemporal lobe and horn Backward growth to form occipital pole andposterior horn 26. Thalamus and hypothalamus Devolops from diencephalon Lateral wall of diencephalon becomesthickened Divided by epithalamic andhypothalamic sulci Epithalamus represented byhabenular and pineal body 27. Corpus striatum Derivative of telencephalon Telencephalic vesicle can besubdivided in to basal part which isthick and superior part is thin Some cells migrate in to marginallayer and forms cortex and remainingcells form copus striatum Corpus striatum subdivided intomedial and lateral divisions 28. Contd.. Fibers descending from cerebralcortex passes through medial andlateral parts constitutes internalcapsule Medial or deeper part form caudatenucleus and superficial or lateral partforms lentiform nucleus 29. Cerebral cortex Formed by migration of cells from themantle layer in to overlying marginallayer Region of insula relatively slow ingrowth and gradually overgrown byadjacent area forms the opercula Cortex divided in to Hippocampal Pyriform neocortex 30. Contd.. Pyriform cortex that recives olfactorysensation constitutes uncus,parahippocampal gyrus and anteriorperforated substance Telencephalon has a medial wallopposing each other gives rise tohippocampal cortex Pyriform cortex arises from marginallayer superficial to corpus striatum With formation of inferior hornhippocampus follows the curve andassumes aring shaped configuration 31. Contd.. Superior part of the hippocampusbecomes ridimentary and formsindesium gresium White matter of the cerebral cortex isformed by projection, association,commisural and ascending fibers 32. Cerebral commisures Part of the neural tube that closes thecranial end of prosencephalon islamina terminalis Anterior commisure Hippocampal commisure Corpus collosum Optic chiasma, habenular commisure,posterior commisure. 33. Autonomic nervous system Sympathetic nervous system Parasympathetic nervous system 34. Sympathetic nervous system Preganglionic neurons devolop frommantle layer of thoracolumbar regionof the spinal cord Located in lateral horn of the cord After short course in the spinalnervethey leave them and growstowards the postganglionic neurons 35. Contd.. Postganglionic neurons are of twotypes Sympathetic trunk Visceral ganglia 36. Parasympathetic nervoussystem Cranial parasympathetic out flow Derived GVE nuclear column of the brainstem Edinger westphal nucleus Salivatory nucleus Lacrimatory nucleus Dorsal nucleus of vagus Sacral parasympathetic out flow Preganglionic cells are formed in themantle layer of the spinal cord near thesulcus limitans S2-S4 37. Contd.. Postganglionic neurons lies near theviscera 38. Thank u