1 / 26

CNS DEVELOPMENT

CNS DEVELOPMENT. Stages in Neural Tube Development. Neural plate. Neural folds. Neural tube. Time-Line. Formation of nervous system occurs during the embryonic stage: End of second week to end of eighth week. Time-Line. Superior (anterior or cranial) neuropore closes by day 27.

buzz
Download Presentation

CNS DEVELOPMENT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. CNS DEVELOPMENT

  2. Stages in Neural Tube Development • Neural plate. • Neural folds. • Neural tube.

  3. Time-Line • Formation of nervous system occurs during the embryonic stage: End of second week to end of eighth week.

  4. Time-Line • Superior (anterior or cranial) neuropore closes by day 27. • Inferior (posterior or caudal) neuropore closes by day 30.

  5. Subdivision of Cranial End of Neural Tube • Tripartite brain. • Pentapartite brain.

  6. Tripartite Brain • Prosencephalon. • Mesencephalon. • Rhombencephalon.

  7. Pentapartite Brain • Prosencephalon: Telencephalon (most anterior). Diencephalon. • Mesencephalon. • Rhombencephalon: Metencephalon. Myelencephalon.

  8. Telencephalon Primordia • Lumina: Lateral ventricles (I, II). • Floor: Basal ganglia (nuclei). Olfactory lobes and nerves. • Roof: Cerebral hemispheres.

  9. Diencephalon Primordia • Lumen: Third ventricle. • Roof: Epithalamus. • Walls: Thalamus. • Floor: Hypothalamus and infundibulum.

  10. Mesencephalon Primordia • Lumen: Cerebral aqueduct (of Sylvius). • Roof =Tectum: Superior and inferior colliculi. • Floor: Tegmentum.

  11. Metencephalon Primordia • Lumen: Part of fourth ventricle. • Roof: Cerebellum. • Floor: Pons.

  12. Myelencephalon Primordia • Lumen: Rest of fourth ventricle. • Main part: Medulla oblongata. • Roof: Posterior choroid plexus.

  13. Histogenesis of Neural Tube • Initial tube wall = Pseudostratified epithelium: Single layer of cells, but cells are of different heights. All cells are in contact with a basement membrane. • Outermost membrane = External limiting membrane.

  14. Histogenesis of Neural Tube • Some neuroepithelial cells remain attached to the basement membrane and will form a single layer of ependymal cells that will line the entire ventricular system and the neural canal.

  15. Histogenesis of Neural Tube • Tube differentiates into two concentric rings by day 26: Mantle layer and marginal layer.

  16. Histogenesis of Neural Tube • Other cells lose contact with the basement membrane and will migrate past the ependymal cells to form a new outer layer of densely packed cells collectively called the: Mantle layer: • Cells that make up the mantle layer are: NEUROBLASTS. • Note that mantle layer is still covered by the external limiting membrane.

  17. Histogenesis of Neural Tube • Neuroblasts in the mantle layer will begin to grow processes (axons) that will form a new outer layer: Marginal layer. The marginal layer is also located beneath the external limiting membrane. • The marginal layer will form the white matter of the spinal cord and the brain. • The mantle layer forms the gray matter of the brain and spinal cord (except for the cortices).

  18. DEVELOPMENTAL ANOMALIES

  19. Anencephaly • Failure of cranial end of neural tube to close.

  20. Arnold-Chiari deformity • Inferior cerebellum and medulla are elongated and protrude into vertebral canal. • Medulla and pons are small and deformed. • Hydrocephalus. • Malformation of lower cranial nerves: Deafness. Tongue, facial muscle, lateral eye movement weakness.

  21. Spina Bifida Occulta • Results from a failure of the inferior neuropore to close. • Vertebral arch(-es) fails to develop in caudal area. • Spinal cord function is usually normal.

  22. Spina Bifida Cystica • Characterized by a sac-like cyst at the caudal end of spine. • Spinal cord and/or meninges may be found in the cyst. • Spinal cord function may be impaired. • May be lower extremity dysfunction. • Bladder and bowel function may be impaired.

  23. Meningocele • Form of spina bifida cystica. • Only meninges found in sac. • Spinal cord function may be impaired. • Signs and symptoms vary depending on location and severity of malformation.

  24. Meningomyelocele • Form of spina bifida cystica. • Both meninges and spinal cord are found in sac. • Always results in abnormal growth of spinal cord. • Lower extremity paralysis. • Bowel and bladder dysfunction. • Loss of sensation to lower limbs.

  25. Myeloschisis • Failure of caudal neural folds to close. • Most severe of the defects.

  26. Holoprosencephaly • Failure of prosencephalon to divide into two cerebral hemispheres. • Often associated with facial deformities: Single orbit with two eyes or one eye or no eye. Proboscis-type nose located above eye. Cleft lip and palate.

More Related