The development of the human body; a manual of human embryology . Fig. 69.—Mature Placenta after Separation from the Uterus. c, Cotyledons; ch, chorion, amnion, and decidua vera; um, umbilical cord.—(Kollmann.) The changes which occur during the later stages ofdevelopment in the chorion are very similar to those de-scribed for the villi. Thus, the mesoderm thickens, itsoutermost layers becoming exceedingly fibrillar in struc-ture, while the ectoderm differentiates into two layers,the outer of which is syncytial while the inner is cellular,and later still, as in the villi, the syncytial layer d
The development of the human body; a manual of human embryology . Fig. 69.—Mature Placenta after Separation from the Uterus. c, Cotyledons; ch, chorion, amnion, and decidua vera; um, umbilical cord.—(Kollmann.) The changes which occur during the later stages ofdevelopment in the chorion are very similar to those de-scribed for the villi. Thus, the mesoderm thickens, itsoutermost layers becoming exceedingly fibrillar in struc-ture, while the ectoderm differentiates into two layers,the outer of which is syncytial while the inner is cellular,and later still, as in the villi, the syncytial layer degener-ates in irregular patches into a peculiar form of fibrin THE H7 which is traversed by flattened anastomosing spaces andto which Minot has applied the name canalized fibrin(Fig. 70).The Deciduae.—In connection with the phenomenon of ,*?&&???? ?*? ,.*&& mes. Fig. 70.—Section through the Placentae Chorion of an Embryo of Seven , Cell layer; ep, remnants of epithelium; fb, fibrin layer; mes, meso-derm.—(Minot.) menstruation periodic alterations occur in the mucousmembrane of the uterus. If during one of these periodsa fertilized ovum reaches the uterus, the desquamation of I48 THE DEVELOPMENT OF THE HUMAN BODY. portions of the epithelium does not occur nor is there anyappreciable hemorrhage into the cavity of the uterus,the uterine mucosa remains in what is practically the ante-menstrual condition until the conclusion of pregnancy,when, after the birth of the fetus, a considerable portion ofits thickness is expelled from the uterus, forming what is Fig. 71.—Diagram showing the Relations of the Fetal Membranes. Am, Amnion; Ch, chorion; M, muscular wall of uterus; R, decidua reflexa; S, decidua serotina; V, decidua vera; Y, yolk-stalk. termed the deciduce. In other words, the sloughing of theuterine mucosa which concludes the pr
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
