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Fig. 374. Transverse section of dog embryo with ten pairs of primitive segments

Bonnet.

Links: Fig. 374 in text | Fig. 71. Dorsal view of dog embryo with ten pairs of mesodermal somites


The entire nervous system, except the olfactory epithelium and parts of certain ganglia (see p. 422), is derived ontogenetically from an elongated plate of thickened ectoderm, the neural plate. This plate extends longitudinally in the axis of the developing embryo, its position being usually first indicated externally by a median groove, the neural groove (Fig. 372), the edges of the plate being elevated into the neural folds (Fig. 373). The neural folds are continuous around the cephalic end of the plate, but diverge at the caudal end, enclosing between them in this region the blastopore. Even at this stage, the neural plate is usually broader at its cephalic end, thereby indicating already the future differentiation into brain and spinal cord (Fig. 375). The neural folds now become more and more elevated (Fig. 374), presumably due in part to the growth of the whole neural plate, and finally meet dorsally and fuse, thus forming the neural tube (Figs. 52 and 391). The fusion of the lips of the neural plate to form the neural tube usually begins somewhere in the middle region of the plate and thence proceeds both forward and backward (Fig. 83). The last point to close anteriorly is usually considered as marking the cephalic extremity of the neural tube, and is called the anterior neuropore.


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Reference

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.



Cite this page: Hill, M.A. (2024, June 18) Embryology Bailey374.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Bailey374.jpg

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current00:06, 30 January 2011Thumbnail for version as of 00:06, 30 January 2011880 × 490 (75 KB)S8600021 (talk | contribs)==Fig. 374. Transverse section of dog embryo with ten pairs of primitive segments== Bonnet. {{Template:Bailey 1921 Figures}} Category:Neural Category:Dog