File:Foster114.jpg

Fig. 114. Five diagrammatic figures illustrating the formation of the foetal membranes of a mammal

(From Kolliker.)

In 1, 2, 3, 4 the embryo is represented in longitudinal section.

1. Ovurn with zona pellucicla, blastodermic vesicle, and embryonic area.
2. Ovum with commencing formation of umbilical vesicle and amnion.
3. Ovum with amnion about to close, and commencing allantois.
4. Ovum with villous subzonal membrane, larger allantois, and mouth and anus.
5. Ovum in which the mesoblast of the allantois has extended round the inner surface of the subzonal membrane and united with it to form the chorion. The cavity of the allantois is aborted. This fig. is a diagram of an early human ovum.

Legend

d. zona radiata ; d and sz. processes of zona ; sh. subzonal membrane, outer fold of amnion, false amnion ; ch. chorion ; ch. z. chorionic villi ; am. amnion ; ks. head-fold of amnion ; ss. tailfold of amnion ; a. epiblast of embryo ; a. epiblast of non-embryonic part of the blastodermic vesicle ; m. embryonic mesoblast ; m'. non-embryonic mesoblast ; df. area vasculosa ; st. sinus terminalis; dd. embryonic hypoblast; i. non-embryonic hypoblast ; kh. cavity of blastodermic vesicle, the greater part of which becomes the cavity of umbilical vesicle ds. ; dg. stalk of umbilical vesicle ; al. allantois ; e. embryo ; r. space between chorion and amnion containing albuminous fluid ; vl. ventral body wall ; hh. pericardial cavity.

Reference

Foster, M., Balfour, F. M., Sedgwick, A., & Heape, W. (1883). The Elements of Embryology. (2nd ed.). London: Macmillan and Co.

Volume 1 - The History of the Chick: Egg structure and incubation beginning | Summary whole incubation | First day | Second day - first half | Second day - second half | Third day | Fourth day | Fifth day | Sixth day to incubation end | Figures 1

Volume 2 - The History of the Mammalian Embryo: General Development | Embryonic Membranes and Yolk-Sac | Organs from Epiblast | Organs from Mesoblast | Alimentary Canal | Appendix | Figures 2

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