THE DECIDUA 



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fleeted portion is the decidua reflexa; that lining the whole 

 uterine cavity is decidua vera, while that part of the decidua 

 vera intervening between the ovum and the uterine wall is 



FIG. 109. Diagrammatic view of a vertical transverse section of the 

 uterus at the seventh or eighth week of pregnancy. 



c, c, c' , cavity of uterus, 



the decidua, opening at 



is, which becomes the cavity of the ut ^ UU a, 



c, c, the cornua, into the Fallopian tubes, and at c' into the cavity of the cervix, 

 which is closed by a plug of mucus; dv, decidua vera; dr, decidua reflexa, with 

 the sparser villi imbedded in its substance; ds, decidua serotina, involving the 

 more developed chorionic villi of the commencing placenta. The fetus is seen 

 lying in the amniotic sac; passing up from the umbilicus is seen the umbilical 

 cord and its vessels passing to their distribution in the villi of the chorion; also 

 the pedicle of the yolk-sac, which lies in the cavity between the amnion and 

 chonon. (Kirkes after Allen Thomson.) 



the decidua serotina and becomes the maternal part of the 

 placenta. 



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