. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 451 formed embraces about one-half of the circumference of the blastodermic vesicle. With the union of the allantois and diplo- trophoblast, the circulation in the decidua reflexa decreases, and it and the trophoblast in contact with it become membra- naceous. They project into the uterine cavity and obhterate its lumen by meeting, but not fusing with, the mesometrial part of the uterine mucosa. As in the bat, the circulation in the yolk-sac never ceases entirely during pregnancy. The changes in the allantoidean tro
. The physiology of reproduction. Reproduction. FCETAL NUTRITION: THE PLACENTA 451 formed embraces about one-half of the circumference of the blastodermic vesicle. With the union of the allantois and diplo- trophoblast, the circulation in the decidua reflexa decreases, and it and the trophoblast in contact with it become membra- naceous. They project into the uterine cavity and obhterate its lumen by meeting, but not fusing with, the mesometrial part of the uterine mucosa. As in the bat, the circulation in the yolk-sac never ceases entirely during pregnancy. The changes in the allantoidean trophoblast are of the same. Fia. 113.—The extension of the yolk-sac against the lacunar trophoblast in Erinaceua (Hubrecht). The yolk-sac is to the left of the figure, and its villi (Vi.) and blood-vessels () are well seen. Tr,, trophoblast; Trs., trophospongia; Df., layer of deciduofraots; D., decidua, of which the inner layer (£>') has assumed a. more reticulate aspect; Sp., spaces in trophoblast. kind, but they occur later. It occupies a discoid area as in Rodents, but it is on the anti-mesometrial side, the primary decidua reflexa is permanent. The lacunar spaces in it are more comphcated than in the omphaloidean trophoblast, and their walls bulge towards the embryo and interlock with vascular projections of the allantois. Hence the viUi have a complete trophoblastic covering. The extremity of each villus is attached to the maternal decidua by strands of trophoblastic cells. The allantoidean trophospongia develops Uke the omphaloidean, but. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marshall, F. H. A. (Francis Hugh Adam), 1878-1949; Cramer, William, 1878-1945; Lochhead, James. London, New York, Longmans, Green
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
