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One theory is that velamentous cord insertion may arise from the process of placental trophotropism, which is the phenomenon where the placenta migrates towards areas which have better blood flow with advancing gestation. The placenta grows in regions with better blood supply and portions atrophy in regions of poor blood flow.
During early pregnancy, the amnionic epithelium is sparsely covered in microvilli, which increase in number throughout pregnancy. [4] The function of this microvillous surface is associated with a densely-packed glycocalix with anionic binding sites; these are thought to be involved with intra-amnionic lipid synthesis. [ 4 ]
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. [11] [15] Arteries in the decidua are remodelled to increase the maternal blood flow into the intervillous spaces of the placenta, allowing gas exchange and the transfer of nutrients to the ...
Due to the fact that placental mammals and marsupials nourish their developing embryos via the placenta, the ovum in these species does not contain significant amounts of yolk, and the yolk sac in the embryo is relatively small in size, in comparison with both the size of the embryo itself and the size of yolk sac in embryos of comparable developmental age from lower chordates.
Circumvallate placenta is a very rare condition affecting pregnant women. This condition is a placental morphological abnormality, with the placenta being formed during the early periods of pregnancy. Women are able to become pregnant with the onset of ovulation and menstruation in early adolescence, with most women becoming pregnant during ...
The placenta can be defined as an organ formed by the sustained apposition or fusion of fetal membranes and parental tissue for physiological exchange. [1] This definition is modified from the original Mossman (1937) [2] definition, which constrained placentation in animals to only those instances where it occurred in the uterus.
Bleeding and spotting are common during the luteal phase of the menstrual cycle, and early stages of pregnancy, but are unrelated to implantation. Implantation bleeding occurs between 7 and 14 days after fertilization, [ 56 ] and is a small amount of light vaginal bleeding or spotting that can occur in early pregnancy due to the blastocyst ...
The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days. [2] During this stage, the zygote begins to divide, in a process called cleavage. A blastocyst is then formed and implanted in the uterus.