Category:Carnegie Embryo 406

From Embryology

References

Kunitomo K. The development and reduction of the tail and of the caudal end of the spinal cord (1920) Contrib. Embryol., Carnegie Inst. Wash. Publ. 272, 9: 163-198.

Embryo No. 406, 16 mm Crown-Rump Length

Kunitomo K. The development and reduction of the tail and of the caudal end of the spinal cord (1920) Contrib. Embryol., Carnegie Inst. Wash. Publ. 272, 9: 163-198.

A graphic reconstruction of embryo No. 406 is shown in figure 37, and a more diagranunatic sketch in figure 9. These show that the embryo has 36 cartilaginous vertebrae. On the right side the thirty-second and thirty-third segments have fused together. The last vertebra consists of two or three sections, each of which in an earlier stage probably represented a complete somite, these later fusing into one large segment. At the caudal end of this is a group of undifferentiated mesodermal cells - the primordium of the caudal ligament. The caudal end of the chorda dorsalis emerges at the thirty-sixth vertebra and terminates abruptly between the vertebral column and the spinal cord. The spinal cord narrows suddenly at the thirty-fourth vertebra. On the ventral wall of the canal in this narrow or atrophic portion of the cord there are three or four folds (fig. 37). In some of the sections can be seen a larger fold at the level of the twenty-ninth vertebra, which hangs down to the level of the thirty-fourth, both sides adhering to the wall of the spinal cord, thus forming a diverticulum, which is not shown in the illustration. The caudal end of the embryo is bent sharply dorsal, the bent portion being marked off on the surface by a shallow, circular furrow. The spinal cord extends to the end of the tail, conforming to the shape of the bent portion. The extreme end contains a narrow cavity which represents the caudal end of the central canal; the canal is interrupted at the root of the tail, where the cord appears to consist of solid nerve-tissue, as is indicated in figure 37. In this specimen there are 31 spinal ganglia with distinct nerves.


Cite this page: Hill, M.A. (2019, July 16) Embryology Carnegie Embryo 406. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Category:Carnegie_Embryo_406

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