The practice of obstetrics, designed for the use of students and practitioners of medicine . ed. Thechorion, since it takes its origin primarilyfrom the zona pellucida, is single when thetwins are derived from two nuclei withina single ovum, but double when theyoriginate from separate ova. Originallythe amnion is always double, for it iselaborated as an outgrowth extending fromthe embryo itself. When twins are in onecommon membrane, there has been, asnoted before, an absorption of the septumwhich, for a time, served as a barrier (, 185, and 186). Placenta.—Primarily the placenta isdoub
The practice of obstetrics, designed for the use of students and practitioners of medicine . ed. Thechorion, since it takes its origin primarilyfrom the zona pellucida, is single when thetwins are derived from two nuclei withina single ovum, but double when theyoriginate from separate ova. Originallythe amnion is always double, for it iselaborated as an outgrowth extending fromthe embryo itself. When twins are in onecommon membrane, there has been, asnoted before, an absorption of the septumwhich, for a time, served as a barrier (, 185, and 186). Placenta.—Primarily the placenta isdouble, for each fetus produces its ownallantois and the placental region result-ing therefrom. In the case of twins com-ing from different ova, the placenta mayremain separate, but even in this casefusion of the placental areas finally occurs. There is almost without excep-tion an anastomosis of the vessels of the placentae of single-egged twins,consequently the placentae are fused to a certain extent, and there resultsa common area of nutrition for both fetuses; while there are two other. Fig. 184.—Twin Pregnancy Result-ing FROM Two Ova from the SameOR Different Graafian Follicles AND FROM THE SaME OR OPPOSITE Ovaries. First arrangement of fetalstructures. , Amnion. Theheavy black portion indicates thechorion.—(Dakin.) DECIDUA SEROTINA - DECIDUASEROTI DECIDUASEROTINA
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectobstetrics, bookyear1
