File:Hertig1956 fig48.jpg

Fig. 48.

Two villous ova of 16 to 17 days of age. Streeter Horizon VII encompasses that developmental stage characterized by branching villi and an axis of the germ disc, whereas Horizon VIII includes that stage characterized by Hensen’s node and primitive groove. The younger of these two ova has not only branching villi and a well-defined axis of the germ disc, but also a definite primitive streak (although not a very distinct primitive groove) and the first beginnings of a head process. Heuser et. al. when reporting this specimen in detail (K15) observed the apparent overlapping of the criteria listed for Horizon VII. and VIII, and considered the younger specimen (7802) an advanced member of Horizon VII. The embryo of the older specimen as yet has not been studied in detail and ultimately may well be placed at least. in Horizon VIII. in this publication our primary interest is in the extra-embryonic structures of these ova.

48 A surface view of an intact 16-day ovum. Note coarsely wrinkled and undulating appearance. of endometrial surface, the dome-shaped elevation of ovum and the blood clot of maternal origin. Carnegie 7802, Sequence 5. X 8.

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Reference

Hertig AT. Rock J. and Adams EC. A description of 34 human ova within the first 17 days of development. (1956) Amer. J Anat., 98:435-493.

Cite this page: Hill, M.A. (2024, April 27) Embryology Hertig1956 fig48.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Hertig1956_fig48.jpg

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