Category:Carnegie Embryo 991

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. 991, 17 mm Crown-Rump Length

The caudal end of embryo No. 991 is somewhat torn, but I feel reasonably sure that it did not exhibit a long caudal process. At a level between the thirty-second and thirty third vertebrae the central canal of the spinal cord narrows suddenh^, and on the ventral wall of the atrophic portion of the cord are two folds. There are only 31 spinal ganglia, the first cervical on each side being absent. The others are completely developed, and even the thirty-first has its full complement of nerve-fibers. In embryo No. 576, just described, this nerve was quite slender. The chorda dorsalis runs in a straight line through the cartilaginous vertebral column and emerges from the thirty-fourth vertebra without winding. This is the first specimen of the series that lacks the non-vertebrated tail. At the point where the tail is found in younger embryos this has a small projection resembhng a tail-bud more than an actual tail. Between the last vertebra and this caudal projection is a mesodermic cell-mass into which enter the plexiform branches of the middle sacral artery and vein.


Cite this page: Hill, M.A. (2019, October 17) Embryology Carnegie Embryo 991. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Category:Carnegie_Embryo_991

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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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