Placenta definition | Dictionary.com

pla⋅cen⋅ta

[pluh-sen-tuh]

–noun, plural -tas, -tae [-tee]

1.	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.

Botany.

a.	the part of the ovary of flowering plants that bears the ovules.

b.	(in ferns and related plants) the tissue giving rise to sporangia.

Origin:
1670–80; < NL: something having a flat, circular form, L: a cake < Gk plakóenta, acc. of plakóeis flat cake, deriv. of pláx (gen. plakós) flat

Related forms:

pla⋅cen⋅tal, plac⋅en⋅tar⋅y [plas-uh

n-ter-ee, pluh-sen-tuh-ree]

, adjective

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
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pla·cen·ta (plə-sěn'tə)

n. pl. pla·cen·tas or pla·cen·tae (-tē)

1. A membranous vascular organ that develops in female mammals during pregnancy, lining the uterine wall and partially enveloping the fetus, to which it is attached by the umbilical cord. Following birth, the placenta is expelled.
2. An organ with similar functions in some nonmammalian animals, such as certain sharks and reptiles.
Botany The part within the ovary of a flowering plant to which the ovules are attached.

[New Latin, from Latin, flat cake, alteration of Greek plakoenta, from accusative of plakoeis, flat, from plax, plak-, flat land, surface; see plāk-¹ in Indo-European roots.]
pla·cen'tal adj.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Placenta

Pla*cen"ta\, n.; pl. L. Placent[ae], E. Placentas. [L., a cake, Gr. ? a flat cake, from ? flat, fr. ?, ?, anything flat and broad.]

1. (Anat.) The vascular appendage which connects the fetus with the parent, and is cast off in parturition with the afterbirth.

Note: In most mammals the placenta is principally developed from the allantois and chorion, and tufts of vascular villi on its surface penetrate the blood vessels of the parental uterus, and thus establish a nutritive and excretory connection between the blood of the fetus and that of the parent, though the blood itself does not flow from one to the other.

2. (Bot.) The part of a pistil or fruit to which the ovules or seeds are attached.

Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.
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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.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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placenta

1677, from Mod.L. placenta uterina "uterine cake" (so called 16c. by It. anatomist Realdo Colombo), from L. placenta "flat cake," from Gk. plakoenta, accusative of plakoeis "flat," related to plax "anything flat," from PIE *plak-, extended form of base *pele- (see plane (n.)). So called from the shape.

Online Etymology Dictionary, © 2001 Douglas Harper
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Main Entry: pla·cen·ta
Pronunciation: pl&-'sent-&
Function: noun
Inflected Form: plural pla·centas or pla·cen·tae /-'sent-(")E/
: the vascular organ in mammals except monotremes and marsupials that unites the fetus to the maternal uterus and mediates itsmetabolic exchanges through a more or less intimate association of uterine mucosal with chorionic and usually allantoic tissues permitting exchange of material by diffusion between the maternal andfetal vascular systems but without direct contact between maternal and fetal blood and typically involving the interlocking of fingerlike vascular chorionic villi with corresponding modified areas ofthe uterine mucosa —see ABRUPTIO PLACENTAE

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 (plə-sěn'tə) Pronunciation Key

The sac-shaped organ that attaches the embryo or fetus to the uterus during pregnancy in most mammals. Blood flows between mother and fetus through the placenta, supplying oxygen and nutrients to the fetus and carrying away fetal waste products. The placenta is expelled after birth.
The part of the ovary of a flowering plant to which the ovules are attached. In a green pepper, for example, the whitish tissue to which the seeds are attached is the placenta.

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