[pluh-sen-tuh] /pləˈsɛn tə/

noun, plural placentas, placentae
[pluh-sen-tee] /pləˈsɛn ti/ (Show IPA)
Anatomy, Zoology. the organ in most mammals, formed in the lining of the uterus by the union of the uterine mucous membrane with the membranes of the fetus, that provides for the nourishment of the fetus and the elimination of its waste products.

(esp of animals) having a placenta: placental mammals See also eutherian
noun (pl) -tas, -tae (-tiː)
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 See also afterbirth
the corresponding organ or part in certain mammals


1808, from Modern Latin placentalis, from placenta (see placenta).

1670s of plants, 1690s of mammals, from Modern Latin placenta uterina “uterine cake” (so called 16c. by Italian anatomist Realdo Colombo), from Latin placenta “a cake, flat cake,” from Greek plakoenta, accusative of plakoeis “flat,” related to plax (genitive plakos) “level surface, anything flat,” from PIE *plak- (1) “to be flat” (cf. Greek plakoeis “flat,” Lettish plakt “to become flat,” Old Norse flaga “layer of earth,” Norwegian flag “open sea,” Old English floh “piece of stone, fragment,” Old High German fluoh “cliff”), extended form of root *pele- (2) “flat, to spread” (see plane (n.1)). So called from the shape.

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.
pla·cen’tal adj.

placenta [(pluh-sen-tuh)]

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.


Read Also:

  • Placental barrier

    placental barrier n. The semipermeable layer of tissue in the placenta that serves as a selective membrane to substances passing from maternal to fetal blood.

  • Placental circulation

    placental circulation n. Circulation of blood through the placenta during intrauterine life, serving fetal needs for aeration, absorption, and excretion.

  • Placental dystocia

    placental dystocia n. The retention or difficult passage of the placenta following delivery.

  • Placental growth hormone

    placental growth hormone n. See human placental lactogen.

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