placenta

American  

[pluh-sen-tuh] / pləˈsɛn tə /

noun

placentas, plural placentae plural

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.

2. Botany.

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

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

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placenta British  

/ pləˈsɛntə /

noun

1. 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

2. the corresponding organ or part in certain mammals

3. botany

   1. the part of the ovary of flowering plants to which the ovules are attached

   2. the mass of tissue in nonflowering plants that bears the sporangia or spores

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placenta Scientific  

/ plə-sĕn′tə /

1. 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.

2. 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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placenta Cultural  

1. 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.

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Other Word Forms

• interplacental
  adjective
• nonplacental
  adjective
• placental
  adjective
• placentary
  adjective
• preplacental
  adjective
• subplacenta
  noun
• subplacental
  adjective

Etymology

Origin of placenta

First recorded in 1670–80; from New Latin: “something having a flat, circular form,” Latin: “cake,” from Greek plakóenta, accusative of plakóeis “flat cake,” derivative of pláx (stem plak- ) “flat”

Explanation

The organ that provides nourishment to developing fetuses before they're born is called a placenta. Most mammals get their nutrients from their mother through the placenta until birth; then they have to look elsewhere... The placenta is commonly called the afterbirth, since it's expelled from the mother's body after a baby is born. A placenta has the unique position of acting as a temporary organ, growing along with the fetus (or fetuses) it feeds, but completely unnecessary after birth. Human placentas are round and flat, and maybe that's why they got their name from the Latin for "cake," placenta.

Example Sentences

All newborns lack vitamin K. No matter how much vitamin K a mother consumes, it doesn’t sufficiently pass through the placenta, and breast milk contains only small amounts.

From Salon • May 7, 2026

Late in her third trimester, doctors diagnosed her with placenta accreta, a potentially life-threatening condition in which the placenta grows too far into the wall of the uterus.

From The Wall Street Journal • Dec. 28, 2025

They have already been detected in breast milk and in the placenta -- and even in the brain.

From Science Daily • Dec. 22, 2025

"It was the knitting needle I brought back from my parents' house. It was also that when I finally miscarried, I didn't know that there would be a placenta to pass."

From BBC • Dec. 12, 2025

In experimental animals the chlorinated hydrocarbon insecticides freely cross the barrier of the placenta, the traditional protective shield between the embryo and harmful substances in the mother’s body.

From "Silent Spring" by Rachel Carson

Related Words

• sheath
• sheet