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As the chorion grows, the chorion laeve comes in contact with the decidua parietalis and these layers fuse. The villi at the embryonic pole, which is in contact with the decidua basalis, increase greatly in size and complexity, and hence this part is named the chorion frondosum. [2]
In humans, the placenta develops in the following manner. Chorionic villi (from the embryo) on the embryonic pole grow, forming chorion frondosum. Villi on the opposite side (abembryonic pole) degenerate and form the chorion laeve (or chorionic laevae), a smooth surface. The endometrium (from the mother) over the chorion frondosum (this part of ...
The gestational sac is spherical in shape, and is usually located in the upper part (fundus) of the uterus.By approximately nine weeks of gestational age, due to folding of the trilaminar germ disc, the amniotic sac expands and occupy the majority of the volume of the gestational sac, eventually reducing the extraembryonic coelom (the gestational sac or the chorionic cavity) to a thin layer ...
Placental mammals, including humans, have a chorioallantoic placenta that forms from the chorion and allantois. In humans, the placenta averages 22 cm (9 inch) in length and 2–2.5 cm (0.8–1 inch) in thickness, with the center being the thickest, and the edges being the thinnest. It typically weighs approximately 500 grams (just over 1 lb).
The chorioallantoic membrane (CAM), also known as the chorioallantois, is a highly vascularized membrane found in the eggs of certain amniotes like birds and reptiles.It is formed by the fusion of the mesodermal layers of two extra-embryonic membranes – the chorion and the allantois. [1]
The placenta derives from the embryonic chorion (the portion of the chorion that develops villi) and the underlying uterine tissue of the mother. [ 4 ] [ 5 ] The corresponding structure in non-mammalian animals is an undifferentiated ball of cells called the blastula .
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Amniotes are distinguished from the other living tetrapod clade — the non-amniote lissamphibians (frogs/toads, salamanders/newts and caecilians) — by the development of three extraembryonic membranes (amnion for embryonic protection, chorion for gas exchange, and allantois for metabolic waste disposal or storage), thicker and keratinized ...