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The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation.It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal ...
Trophoblasts are specialized cells of the placenta that play an important role in embryo implantation and interaction with the decidualized maternal uterus. [5] The core of placental villi contain mesenchymal cells and placental blood vessels that are directly connected to the fetus’ circulation via the umbilical cord.
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 cytotrophoblast secretes proteolytic enzymes to break down the extracellular matrix between the endometrial cells to allow finger-like projections of trophoblast to penetrate through. Projections of cytotrophoblast and syncytiotrophoblast pull the embryo into the endometrium until it is fully covered by endometrial epithelium, save for the ...
It modifies the metabolic state of the mother during pregnancy to facilitate energy supply to the fetus. hPL has anti-insulin properties. hPL is a hormone secreted by the syncytiotrophoblast during pregnancy. Like human growth hormone, hPL is encoded by genes on chromosome 17q22-24. It was identified in 1963. [2]
[7] [8] This protects the fetus and placenta from oxidative stress during early development in the histiotrophic (glandular nutrition) stage. As fetal nutrition switches to the hemotrophic (blood-derived nutrition) stage, EVT plugs dissolve and perfusion of maternal blood begins, allowing further development of both the fetus and placenta.
They also secrete preimplantation factor, a peptide that helps their invasion and placenta formation. [27] As these trophoblasts penetrate, they fuse with their neighbours, terminally differentiating into a multinucleated tissue, a syncytium known as the syncytiotrophoblast. Between this layer and the blastocyst lies the cytotrophoblast. [28] [29]
The presence of hCG in a woman's body indicates that a fertilized egg has implanted in the uterus and the placenta has started to form. 10 days after fertilization, significant hCG can be detected from woman's blood sample. [6] The levels of hCG in the body increase rapidly in the first few weeks of pregnancy, doubling every 48–72 hours. [7]