Development of nervous system
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well describes the development of nervous system from basic to advanced concept including neural tube defects. the concepts are presented in graphical form for easy understanding of concepts.
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Development of nervous system
- 1. To MBBS 2nd year Dr Laxman Khanal Assistant Professor, Department of Anatomy BPKIHS, Dharan, Nepal 12-02-2017 Development of nervous system
- 2. Cranial nerves 1. Motor parts 2. Sensory parts 3. Autonomic parts Parasympathetic Spinal nerves 1. Motor parts 2. Sensory parts 3. Autonomic parts A. Sympathetic (thoracic and lumbar segment) B. Parasympathetic (sacral segment) Parts of nervous system 1. CNS- brain and spinal cord 2. PNS- cranial and spinal nerve 3. ANS- contributed by both CNS and PNS ANS -cardiac muscle, smooth muscle and glands.
- 3. Notochord acts as an inducer for development of nervous system. BMP • Ectoderm • Neuroectoderm • Neural plate • Neural fold • Neural groove • Neural tube Neuroectoderm Neural tube Edge of Neuroectoderm and embryonic ectoderm Neural crest cells Embryonic ectoderm Ectodermal derivatives
- 4. Development of neural crest cells Epithelial Mesenchymal E- Cadherin
- 5. Pharyngeal arch derivatives • Skeletal component • Nerves and ganglia of each arch • Dermis overlying each arch • Blood vessels of face. Migration of neural crest cells
- 6. Cranial neuropore Closure at 25th day Caudal neuropore Closure at 27th day Brain SC Alpha feto protein (AFP) increases in maternal AF if neuropores fail to close (neural tube defects).
- 7. Anencephaly Craniorachischisis Neural tube defects of cranial part of neural tube
- 8. Neural tube defects of caudal part of neural tube Rachischisis Myelomeningocele Spina bifida occulta
- 9. Prevented by maternal use of folic acid prior to and during pregnancy. Spina bifida occulta Meningocele Myelomeningocele Rachischisis
- 10. Anterior portion of neural tube forms three primary brain vesicles. 1. Prosencephalon: Telencephalon + Diencephalon 2. Mesencephalon: 3. Rhombencephalon: Metencephalon + Mylencephalon I & II CN III & IV CN V- XII CN
- 11. Development of ventricular system 4th
- 12. Development of spinal cord L TS neural tube Neuroepithelial cells L Neuroblast cell L Mantle cell layer Marginal cell layer L A B A B R F Anterior horn Posterior horn intermediate horn Sensory Motor Autonomic
- 13. Neuroblast Glioblast Microglial cells Ependymal cells Origin of various types of cells
- 14. Brain stem Arrangement of alar and basal plate is intact but the arrangement is different. Higher center Basal plate regress and alar plate accentuate. A B
- 15. G S E S V E G V E Development of functional columns in brain stem Basal plate – motor components Skeletal muscle 1. Somatic muscles - GSE 2. Pharyngeal arch muscles- SVE Smooth muscle- GVE (autonomic) CN supplying somatic skeletal muscles Motor nerve of pharyngeal arch CN with parasympathetic actions
- 16. G S E S V E G V E G S A S V A G V A S S A Development of functional columns in brain stem Alar plate- sensory column Senses • General senses • Special sense- taste • Senses from viscera • Special sense-hearing & Eqb Pain, touch, temperature, pressure Taste Sense of distension of viscera Hearing & equilibrium
- 17. Mesencephalic flexure Cervical flexure Pontine flexure Rhombic lip • Postero-lateral extension of alar plate of metencephalon. • Give rise to cerebellum. Rhombic lip
- 18. TS of caudal part of Pons Rhombic lip Cerebellar plate TS Mesencephalon Alar plate Basal plate Alar plate Sup colliculus Inf colliculus Basal plate Nuclei of 3rd CN Nucleus of 4th CN
- 19. Development of Prosencephalon Diencephalon 3rd ventricle Telencephalon 2 lateral ventricles 1. Thalamus 2. Hypothalamus 3. Epithalamus 4. Subthalamus 5. Metathalamus 6. Neurohypophysis
- 20. Summary • The CNS develops from a dorsal thickening of ectoderm-the neural plate, which appears around the middle of the third week. • The neural plate is induced by the underlying notochord and paraxial mesoderm to form neural tube. • The cranial end of the neural tube forms the brain and the remainder forms the spinal cord. • The neural canal, the lumen of the neural tube, becomes the ventricles of the brain and the central canal of the spinal cord. • Defects in the closure of the neural tube (NTDs) account for most severe anomalies of nervous system.