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UROGENITAL SYSTEM 



FIG. 234. Diagrammatic section through a pregnant uterus at the seventh or eighth week (after 

 Allen Thomson), c, c, openings of uterine tubes; c', cervix with mucous plug; dv, decidua vera or pari- 

 etalis; dr, decidua capsularis; ds, decidua basalis (serotina); ch, chorion with villi; the villi extending 

 into the decidua basalis are from the chorion frondosum; u, umbilical cord; al, allantois. 



FIG. 235. Diagram illustrating the second phase in the development of the chorionic villi and 

 placenta (after Peters), mes, mesoderm; core, core, of villus about which is the trophectoderm layer; 

 sy, syncytium of trophoderm; mcp, endothelium of maternal capillary; vs, intervillous space. 



