234 



THE UROGENITAL SYSTEM 



FIG. 241. 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 orjparietalis; dr, decidual capsularis; ds, decidua basalis; ch, chorion with villi; the villi 

 extending into the decidua basalis are from the chorion frondosum; am, amnion; , umbilical 

 cord; al, allantois; y,y', yolk sac and stalk. 



sa-pe 



- M csoderm 



Syncytial. 

 Irophodertn* 



Core of villus 





Canalized fibrin Maternal capillary Intcnillous space 



FIG. 242. Diagram illustrating the development of the chorionic villi and placenta (after 



Peters). 



