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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 ...
Identical twins have identical genomes in the immediate aftermath of twinning. About two-thirds of monozygotic twins share the same placenta, arising by cleavage before the fourth day of development; the other third have separate placentas because cleavage has taken place after the fourth day after choriogenesis has begun.
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 ...
Placenta with attached fetal membranes (ruptured at the margin at the left in the image), which consists of the chorion (outer layer) and amnion (inner layer).. The part of the chorion that is in contact with the decidua capsularis undergoes atrophy, so that by the fourth month scarcely a trace of the villi is left.
Nine-week-old human embryo from an ectopic pregnancy. Organogenesis is the development of the organs that begins during the third to eighth week, and continues until birth. Sometimes full development, as in the lungs, continues after birth. Different organs take part in the development of the many organ systems of the body.
In the placenta, the intervillous space is the space between chorionic villi, and contains maternal blood.. The trophoblast, which is a collection of cells that invades the maternal endometrium to gain access to nutrition for the fetus, proliferates rapidly and forms a network of branching processes which cover the entire embryo and invade and destroy the maternal tissues.
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.
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]