Definition of placenta
1 : the vascular organ in mammals except monotremes and marsupials that unites the fetus to the maternal uterus and mediates its metabolic exchanges through a more or less intimate association of uterine mucosal with chorionic and usually allantoic tissues; also : an analogous organ in another animal
2 : a sporangium-bearing surface; especially : the part of the carpel bearing ovules
Recent Examples of placenta from the Web
But once the baby is out, the placenta is no longer needed.
In 2011, Erlich took a close look at the blood of identical twins who shared a placenta during development; early on, these twins are also sharing blood – even as adults, each twin has blood cells with DNA from the other twin.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'placenta'. Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Origin and Etymology of placenta
New Latin, from Latin, flat cake, from Greek plakoenta, accusative of plakoeis, from plak-, plax flat surface — more at fluke
First Known Use: 1638
PLACENTA Defined for English Language Learners
Definition of placenta for English Language Learners
medical : the organ in mammals that forms inside the mother's uterus, nourishes the unborn baby, and is pushed out of the mother after the birth of the baby
PLACENTA Defined for Kids
Definition of placenta for Students
: the organ in most mammals by which the fetus is joined to the uterus of the mother and is nourished
Medical Definition of placenta
: the vascular organ in mammals except monotremes and marsupials that unites the fetus to the maternal uterus and mediates its metabolic 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 and fetal 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 of the uterine mucosa—see abruptio placentae
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