Implantation site, showing the relation of the embryo to the uterine tissues. Streamers of syncytiotrophoblast extend outward into the endometrial stroma. Beyond the tips of the streamers numerous detached or wandering syncytial cells are visible. Beneath the embryo, in close proximity to the syncytium, there are distended uterine glands filled with stagnant blood. Near the lower margin of the picture a blood sinus (Bl. Sin.) is seen filled with plasma and some loosely packed red cells. A large vesicle, presumably a detached part of the primitive yolk sac (P.P.Y.S.), lies on the mesodermal lining of the chorion at the side opposite the embryo. Section 135.
Fig. 3. Heuser et al., 1945.
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Keywords: chorion, embryo, endometrial stroma, implantation site, primitive umbilical vesicle, syncytial cells, syncytiotrophoblast, syncytium, uterine gland
Source: The Virtual Human Embryo.