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Histopathology of acute subchorionic intervillositis, with neutrophils in Langhan’s layer of fibrinoid (by the fetal surface, at the base of a chorionic villus, seen at top right). Placentitis is an inflammation of the placenta. The main forms of placentitis are: Villitis, inflammation of chorionic villi.
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 ...
The region of fibrinoid deposition where trophoblasts meet the compact portion of the decidua basalis is called Rohr's layer, while the fibrinoid deposits that occur between the compact and spongy layer of the decidua basalis is termed Nitabuch's layer (for Raissa Nitabuch). This layer is absent in placenta accreta. [2]
These layers are arranged on top of each other, giving rise to the name trilaminar, or "three-layered". The mesoderm is segmented further into the paraxial, intermediate and the lateral plate mesoderm. These three layers arise early in the third week (during gastrulation) from the epiblast (a portion of the mammalian inner cell mass).
The epiblast gives rise to the three germ layers of the developing embryo during gastrulation (endoderm, mesoderm, and ectoderm). The trophoblast is a layer of cells forming the outer ring of the blastocyst that combines with the maternal endometrium to form the placenta. Trophoblast cells also secrete factors to make the blastocoel. [25]
As the placenta forms and the cytotrophoblast layer grows and extends, distal villous CYT differentiate to cell column CYT which eventually detach and invade deeply to the maternal decidua as interstitial EVTs. [6] These EVTs anchor placental villi to the maternal decidua.
The fetal membranes are derived from the trophoblast layer (outer layer of cells) of the implanting blastocyst. [3] The trophoblast layer differentiates into amnion and the chorion, which then comprise the fetal membranes. [4] The amnion is the innermost layer and, therefore, contacts the amniotic fluid, the fetus and the umbilical cord. [5]
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.