Development of Nervous System : Sylabus for Foreign Students

Department of Histology and Embryology, P. J. Šafárik University, Medical Faculty, Košice

Development of nervous system : Sylabus for foreign students

Author: Prof. MUDr. Eva Mechírová, CSc.

Development of notochord and notochordal process

- by proliferation of epiblast (ectodermal) cells primitive streak develops

- primitive streak grows cranially in the midline of the bilaminar embryonic

disc, elongates and its cranial end proliferates to form the primitive node

- in the primitive streak develops a narrow primitive groove that ends in a

primitive pit

- influence of embryonic growth factors – epiblastic (ectodermal) cells

proliferate and migrate through the primitive groove between epiblast and

hypoblast, spred cranially and laterally and give rise to embryonic mesoderm

- from the cells of primitive node the notochordal process and later notochordal canal is developed – situated in the midline between ecto and endoderm

-ventral wall of notochordal canal disappears and gives rise to a solid cord of cells – the notochord

3rd week- the developing notochord induces the overlying ectoderm to produce the neural plate – situated between primitive node and oropharyngeal membrane

Formation of neural tube

19th day

Development of brain vesicles

Histogenesis of neural tube and neural crest

Development of spinal cord and histogenesis

● growing and thickening of neuroepithelium of neural tube, formation of canalis centralis ● lateral walls produce a groove - sulcus limitans that divides horizontally the spinal cord in:

(A) Ventral part → basal plate → neuroblasts - motor neurons (B) Dorsal part → alar plate → neuroblasts - sensory neurons dorsal wall – roof plate and ventral wall – floor plate

- as the basal plates grow and enlarge, produce ventral median fissure - as the alar plates grow and enlarge, produce dorsal septum and dorsal median sulcus

Spinal cord development

Development of rhombencephalon – hindbrain

- the pontine flexure divides hindbrain into metencephalon and myelencephalon

Metencephalon

- becomes the cerebellum - from the dorsal part of alar plate = cortex cerebelli, nuclei – pontine, cochlear, vestibular, of trigeminal nerve - nerve fibers connecting cortex cerebri and cerebelli in the ventral region form pons Varoli

Myelencephalon

- from the 5th brain vesicle- myelencephalon - gives rise the medulla oblongata and dorsal part of the IV. brain ventricle - neuroblasts of alar plate migrate into marginal zone and form gracile and cuneate nuclei laterally - ventrally are situated the pyramids - tractus corticospinalis - neuroblasts of basal plate develop into motor neurons of nuclei of cranial nerves - lateral walls together with basal and alar plates rotate around longitudinal axis of floor plate (like opening a book) and the roof plate become thiner