Category:Carnegie Embryo 432

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. 432, 18 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.

Embryo No. 432 contains 34 cartilaginous vertebrae. The last is larger than the thirty-third and on its lateral side shows three divisions, each consisting of young precartilaginous tissue. The middle part, where the segments are partially fused, is made up of cartilaginous tissue, and here the vertebra is incompletely divided into two segments - cranial and caudal. A little to one side of the median line, therefore, it is possible to count 35, and more laterally, 36 vertebrae. If the scleromeres of the several somites fuse together and develop into the last cartilagiiious vertebra, we may assume that the remaining mesenchymal somites left in the caudal portion of the tail form the non-vertebrated tail, and that in a more advanced stage of embryonic growth this substance develops into the caudal ligament. The chorda dorsalis shows two branches at its caudal end; one is formed at the thirty-second, the other at the thirty-fourth vertebra, and both follow a dorsal course. The more caudal branch is the longer, and its pointed extremity, which represents the caudal end of the chorda, adheres to the ventral wall of the atrophic portion of the spinal cord, as shown in figure 39. The wall of the spinal cord is quite thick in this region and at its upper portion are several folds. This condition is very interesting on account of its possible mechanical relation to the chorda, because as the caudal end of the chorda retracts it would tend to draw up the end of the spinal cord that is in the tail.


Cite this page: Hill, M.A. (2019, July 22) Embryology Carnegie Embryo 432. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Category:Carnegie_Embryo_432

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

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