|a fool or simpleton; ninny.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|—n , pl -tas, -tae|
|1.||See also afterbirth the vascular organ formed in the uterus during pregnancy, consisting of both maternal and embryonic tissues and providing oxygen and nutrients for the fetus and transfer of waste products from the fetal to the maternal blood circulation|
|2.||the corresponding organ or part in certain mammals|
|a. the part of the ovary of flowering plants to which the ovules are attached|
|b. the mass of tissue in nonflowering plants that bears the sporangia or spores|
|[C17: via Latin from Greek plakoeis flat cake, from plax flat]|
placenta pla·cen·ta (plə-sěn'tə)
n. pl pla·cen·tas or pla·cen·tae (-tē)
The membranous vascular organ in female mammals that permits metabolic interchange between fetus and mother. It develops during pregnancy from the chorion of the embryo and the decidua basalis of the maternal uterus and permits the absorption of oxygen and nutritive materials into the fetal blood and the release of carbon dioxide and nitrogenous waste from it, without the direct mixing of maternal and fetal blood. It is expelled following birth.
|placenta (plə-sěn'tə) Pronunciation Key
An organ that forms in the uterus after the implantation of a zygote. The placenta moves nourishment from the mother's blood to the embryo or fetus; it also sends the embryo or fetus's waste products into the mother's blood to be disposed of by the mother's excretory system. The embryo or fetus is attached to the placenta by the umbilical cord. After birth, the placenta separates from the uterus and is pushed out of the mother's body.