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The chorionic villi are at first small and non-vascular. 13–15 days: trophoblast only [1] Secondary: The villi increase in size and ramify, while the mesoderm grows into them. 16–21 days: trophoblast and mesoderm [1] Tertiary: Branches of the umbilical artery and umbilical vein grow into the mesoderm, and in this way the chorionic villi are ...
In humans it is formed by extraembryonic mesoderm and the two layers of trophoblast that surround the embryo and other membranes; [1] the chorionic villi emerge from the chorion, invade the endometrium, and allow the transfer of nutrients from maternal blood to fetal blood.
The chorionic membrane is a fibrous tissue layer containing the fetal blood vessels. [4] Chorionic villi form on the outer surface of the chorion, which maximise surface area for contact with maternal blood. [4] The chorionic villi are involved in fetal-maternal exchange. [10]
Chorionic villi (right of image) and cartilage, i.e. fetal parts (left of image). H&E stain. Products of conception, abbreviated POC, is a medical term used for the tissue derived from the union of an egg and a sperm. It encompasses anembryonic gestation (blighted ovum) which does not have a viable embryo.
In this type of placentation, the chorionic villi are in contact with the endothelium of maternal blood vessels. (e.g. in most carnivores like cats and dogs) epitheliochorial placentation Chorionic villi, growing into the apertures of uterine glands ( epithelium). (e.g. in ruminants, horses, whales, lower primates, dugongs) hemochorial placentation
The villi begin to branch and contain blood vessels of the embryo. Other villi, called terminal or free villi, exchange nutrients. The embryo is joined to the trophoblastic shell by a narrow connecting stalk that develops into the umbilical cord to attach the placenta to the embryo.
In developmental biology, choriogenesis is the formation of the chorion, an outer membrane of the placenta that eventually forms chorionic villi that allow the transfer of blood and nutrients from mother to fetus. [1]
Image showing trophoblast differentiated into the two layers of cytotrophoblast and syncytiotrophoblast during implantation. It is the outer layer of the trophoblasts and actively invades the uterine wall, during implantation, rupturing maternal capillaries and thus establishing an interface between maternal blood and embryonic extracellular fluid, facilitating passive exchange of material ...