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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 ...
The decidua is the modified mucosal lining of the uterus (that is, modified endometrium) that forms every month, in preparation for pregnancy. It is shed off each month when there is no fertilized egg to support. [1] The decidua is under the influence of progesterone. Endometrial cells become highly characteristic.
On gross pathology, the presence of chorionic villi (left) is diagnostic of products of conception, whereas decidua (right) is not. The diagnosis is based on clinical presentation, quantitative HCG, ultrasound, and pathologic evaluation. A solid, heterogeneous, echogenic mass has a positive predictive value of 80%, but is present in only a ...
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]
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] Thus the placenta develops from the chorion frondosum and the decidua basalis.
Increta – chorionic villi invaded into the myometrium. Percreta – chorionic villi invaded through the perimetrium (uterine serosa ). Because of abnormal attachment to the myometrium, placenta accreta is associated with an increased risk of heavy bleeding at the time of attempted vaginal delivery.
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 ...
The form of the human placenta is generally classified as a discoid placenta. Within this, the cotyledons are the approximately 15-25 separations of the decidua basalis of the placenta, separated by placental septa. [3] Each cotyledon consists of a main stem of a chorionic villus as well as its branches and sub-branches. [3]