242 



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 arc from the chorion frondosum; it, umbilical cord; al, allantois. 



Jib ca vs 



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

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

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



