. The science and art of midwifery. Fig. 47.—1, exocborion ; 2, blastodermicchorion ; ?/, umbilical vesicle ; a, am-nion ; p, pedicle of allantois. in the form of an embankmentAt this time the umbilical vesicle Fig. Fig. 1.—Human embryon, at the ninth week, removed from the membranes; three times the natural size (Erdl).Fig. 2.—Human embryon, at the twelfth week, inclosed in the amnion; natural size (Erdl). DEVELOPMENT OF THE OVUM. 53 is still very large. The allantois, like the umbilical vesicle and theintestine, is composed of two layers derived respectively from the in-ternal layer of
. The science and art of midwifery. Fig. 47.—1, exocborion ; 2, blastodermicchorion ; ?/, umbilical vesicle ; a, am-nion ; p, pedicle of allantois. in the form of an embankmentAt this time the umbilical vesicle Fig. Fig. 1.—Human embryon, at the ninth week, removed from the membranes; three times the natural size (Erdl).Fig. 2.—Human embryon, at the twelfth week, inclosed in the amnion; natural size (Erdl). DEVELOPMENT OF THE OVUM. 53 is still very large. The allantois, like the umbilical vesicle and theintestine, is composed of two layers derived respectively from the in-ternal layer of the blastodermic membrane (entoderm), and the innerstratum of the mesoderm. It speedily becomes vascular, and increasesrapidly in size. The inner surfaces of the sac soon adhere together,so as to form a single membrane. In the course of the third weekthe allantois reaches the chorion, over which it spreads and formsa complete vascular lining. According to the usual acceptation, thevessels of the allantois everywhere penetrate into the villi of thechorion. Then the chorion and allantois fuse together and formby their consolidation a compound membrane termed the permanentchorion* At first the embryo is connecte
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Keywords: ., bookcentury1800, bookdecade1890, bookidsci, booksubjectobstetrics
