American Heritage® Dictionary of the English Language, Fourth Edition
- n. 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.
- n. An organ with similar functions in some nonmammalian animals, such as certain sharks and reptiles.
- n. Botany The part within the ovary of a flowering plant to which the ovules are attached.
Century Dictionary and Cyclopedia
- n. In zoöl., anat., and medicine: The organ of attachment of a vertebrate embryo or fetus to the wall of the uterus or womb of the female. It is a specially modified part of the surface of the chorion or outside one of the fetal envelops, of a flattened circular form, like a plate or saucer, one side of which is closely applied to the wall of the womb, and from the other side of which proceeds the umbilical cord or navel-string. It is highly vascular, and in intimate vital connection with a similarly vascular area of the uterine walls, serving for the interchange of the constituents of the blood between the female and the fetus, and thus acting during in-tra-uterine life as the organ of circulation, respiration, and nutrition of the fetus. The human placenta is about as large as a soup-plate, and in connection with the navel-string and membranes is commonly known as the uterine cake, afterbirth, or secundines. The presence of a true placenta is necessarily restricted to viviparous vertebrates, and does not occur in all of these (the two lower subclasses of mammals, the marsupials and monotremes, being implacental). Several forms of placenta have been distinguished among placental mammals, and made a basis of classification. See also cuts under
embryo and uterus.
- n. In echinoderms, a flat discoidal sea-urchin, as a sand-dollar or cake-urchin: used in a generic sense by Klein, 1734.
- n. [capitalized] A genus of bivalve mollusks, now called Plaruna.
- n. In botany, that part of the ovary of flowering plants which bears the ovules. It is usually the more or less enlarged or modified margins of the carpellary leaves, and is of a soft cellular texture. When the ovary is composed of a single leaf, both margins give rise to ovules, and they are consequently in two rows. In a compound ovary there are various modifications of the placenta. Thus.when the edges of the car-pellary leaes all meet in a common axis, the placentas are said to be axile. When, by obllteration of the dissepiments, such an ovary becomes one-celled, the axile placentas remain in a column as a free central placenta. Or, when the edges of the carpellary leaves barely meet and slightly incurve, the placentas become parietal, being borne on the wall. There are all degrees of incurvation, the placentas being located accordingly. In vascular cryptogams the point giving rise to the sporangia is sometimes called the placenta. The placenta is sometimes termed the trophospermium and spermophorum. See also cut under
- n. anatomy A vascular organ in mammals, except monotremes and marsupials, present only in the female during gestation. It supplies food and oxygen from the mother to the foetus, and passes back waste. It is implanted in the wall of the uterus and links to the foetus through the umbilical cord. It is expelled after birth.
- n. botany In flowering plants, the part of the ovary where ovules develop; in non-flowering plants where the spores develop.
GNU Webster's 1913
- n. (Anat.) The vascular appendage which connects the fetus with the parent, and is cast off in parturition with the afterbirth.
- n. (Bot.) The part of a pistil or fruit to which the ovules or seeds are attached.
- n. the vascular structure in the uterus of most mammals providing oxygen and nutrients for and transferring wastes from the developing fetus
- n. that part of the ovary of a flowering plant where the ovules form
- From Medieval Latin placenta uterina ("uterine cake"), from Latin placenta ("flat cake"), because of the flat round shape of the afterbirth. (Wiktionary)
- 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. (American Heritage® Dictionary of the English Language, Fourth Edition)
“They say the placenta is a rich source of stem cells capable of transforming into many types of cells in the body, holding out the hope of using them to treat many human ailments including spinal-cord injury and diabetes.”
“And unless the little sack [folliculus] of the placenta is the intermediary between the falling blood and the child, [the blood] by penetrating would kill him who is exposed.”
“I had what they called placenta previa and I nearly bled to death and had a terrible time, but while I was in the hospital, soon thereafter, I was very ill and had to have blood transfusions.”
“Turns out I didn't write a newsletter for your 59th month, and I blame that entirely on what I call placenta brain, the situation that occurs when a pregnant woman's blood supply is so concentrated on growing someone else's fingers and toes that her brain doesn't have enough juice to complete simple tasks.”
“In addition, although cows "share" their blood with their unborn calves, the bovine placenta is a natural filter.”
“Exchange of respiratory gases (oxygen and carbon dioxide) across the placenta from the mother to the fetus and from the fetus to the mother.”
“Flow of blood across the placenta from the mother to the fetus and from the fetus to the mother.”
“And, last of all, the first scan showed that, this time, the placenta is placed towards my back, effectively removing a potential frontal shock absorber from the equation.”
“When the placenta grows across the opening of the cervix, it is described as a placenta previa.”
“These abnormalities in attachment of the placenta are called placenta accreta, placenta increta, and placenta percreta, depending on the depth of invasion of the uterine wall.”
These user-created lists contain the word ‘placenta’.
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Looking for tweets for placenta.