placenta

noun pla·cen·ta \ plə-ˈsen-tə \

|Updated on: 30 Jul 2018

Definition of placenta

plural placentas or placentae play \plə-ˈsen-(ˌ)tē\

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

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Recent Examples of placenta from the Web

The researchers studied genes linked to the placenta, the maternal immune system and the fetal liver, and found nine of those genes produce RNA signals that change distinctly as pregnancy progresses.

— pam belluck, New York Times, "Blood Test Might Predict Pregnancy Due Date and Preterm Birth," 7 June 2018
After giving birth, your placenta is supposed to come out.

— rachel epstein, Marie Claire, "Kim Kardashian Posts a Sweet Picture of Saint Snuggling Chicago," 22 May 2018
Toxoplasma courses through the body, targeting any combination of organs, including, in the case of females, the uterus, and for fetuses, the placenta.

— kim steutermann rogers, Smithsonian, "How the Tiniest of Parasites is Taking Down the Mightiest of Monk Seals," 9 July 2018
To make these new experimental blood tests, the Quake team identified and zeroed in on the activity levels of specific genes in the fetus or its placenta.

— dina fine maron, Scientific American, "Blood Test Could Predict Premature Birth Risk, Due Date," 7 June 2018
An obstetrician extracted blood from her umbilical cord and the placenta.

— maria clark, NOLA.com, "New Orleans teen survives cancer thanks to sister's stem cells, shares his story at the Vatican," 6 June 2018
These genes seem to monitor or represent the biological resilience or sensitivity of the placenta to environmental stress.

— mark lieber, CNN, "Pregnancy complications might 'turn on' schizophrenia genes, study says," 30 May 2018
The 108 genes that make up the risk score are expressed at particularly high levels in the placenta, the study also found, and at higher levels in the placentas of male fetuses than female ones.

— sharon begley, STAT, "Schizophrenia ‘risk genes’ are not so risky if the mother’s pregnancy was healthy," 28 May 2018
Instead, plumbers at a clinic in Kerala made a ghastly discovery: A two-day-old baby had been flushed down the toilet, with her placenta still intact.

— amanda erickson, Washington Post, "2-day-old baby girl found flushed down the toilet in India," 16 Apr. 2018

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

NEW! Time Traveler

First Known Use: 1638

in the meaning defined at sense 1

See Words from the same year

PLACENTA Defined for English Language Learners

placenta

noun

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

placenta

noun pla·cen·ta \ plə-ˈsen-tə \

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 Dictionary

placenta

noun pla·cen·ta \ plə-ˈsent-ə \

medical Definition of placenta

plural placentas or placentae play \-ˈsent-(ˌ)ē\

: 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