MEDICAL APPLIED ANATOMY 



THE NERVOUS SYSTEM 



Development of the Nervous System. Before the different 

 parts of the nervous system are described, it is necessary to 

 outline, as briefly as possible, the developmental history of 

 the nervous system as a whole. 



During the first week of intra-uterine life, a longitudinal 



FIG. I. Transverse Section of Human Embryo. 



A. Ectoderm. 



B. Neural groove. 



C. Endoderm. 



D. Mid -gut. 



E Vitello-intestinal duct. 

 F. Yolk-sac. 



groove, which rapidly increases in depth, appears in the 

 ectoderm on the dorsal surface of the human embryo (Fig. i). 

 At a slightly later stage, the edges of the groove coalesce so 

 as to form a tube, which soon loses its connexion with the 

 surface ectoderm. This tube is lined entirely by ectoderm 



