This article is about the temporary organ. For the expulsion of the placenta after birth, see placental expulsion. For equivalent organs in other animals, see Placentalia. For other uses, see Placenta (disambiguation).
For a less technical description, see the Simple English Wikipedia version at simple:Placenta
Placenta
Human placenta from just after birth with the umbilical cord in place
Human placenta shown in uterus connected to fetus with umbilical cord
Details
Precursor
Decidua basalis, chorion frondosum
Identifiers
Latin
placenta
MeSH
D010920
TE
E5.11.3.1.1.0.5
Anatomical terminology
[edit on Wikidata]
The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal physiology during pregnancy.[1] The placenta connects to the fetus via the umbilical cord, and on the opposite aspect to the maternal uterus in a species-dependent manner. In humans, a thin layer of maternal decidual (endometrial) tissue comes away with the placenta when it is expelled from the uterus following birth (sometimes incorrectly referred to as the 'maternal part' of the placenta). Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development.[2]
Mammalian placentas probably first evolved about 150 million to 200 million years ago. The protein syncytin, found in the outer barrier of the placenta (the syncytiotrophoblast) between mother and fetus, has a certain RNA signature in its genome that has led to the hypothesis that it originated from an ancient retrovirus: essentially a virus that helped pave the transition from egg-laying to live-birth.[3][4][5]
The word placenta comes from the Latin word for a type of cake, from Greek πλακόεντα/πλακοῦντα plakóenta/plakoúnta, accusative of πλακόεις/πλακούς plakóeis/plakoús, "flat, slab-like",[6][7] with reference to its round, flat appearance in humans. The classical plural is placentae, but the form placentas is more common in modern English.
^Jin M, Xu Q, Li J, Xu S, Tang C (September 2022). "Micro-RNAs in Human Placenta: Tiny Molecules, Immense Power". Molecules. 27 (18): 5943. doi:10.3390/molecules27185943. PMC 9501247. PMID 36144676.
^Pough FH, Andrews RM, Cadle JE, Crump ML, Savitsky AH, Wells KD (2004). Herpetology (3rd ed.). Pearson. ISBN 978-0-13-100849-6.[page needed]
^Mitra A (31 January 2020). "How the placenta evolved from an ancient virus". WHYY. Retrieved 9 March 2020.
^Chuong EB (October 2018). "The placenta goes viral: Retroviruses control gene expression in pregnancy". PLOS Biology. 16 (10): e3000028. doi:10.1371/journal.pbio.3000028. PMC 6177113. PMID 30300353.
^Villarreal LP (January 2016). "Viruses and the placenta: the essential virus first view". APMIS. 124 (1–2): 20–30. doi:10.1111/apm.12485. PMID 26818259. S2CID 12042851.
^Henry George Liddell, Robert Scott, "A Greek-English Lexicon", at Perseus Archived 2012-04-05 at the Wayback Machine.
^"placenta" Archived 2016-01-30 at the Wayback Machine. Online Etymology Dictionary.
The placenta (pl.: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation...
Placenta praevia is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding...
edges of the placenta. After delivery, a circumvallate placenta has a thick ring of membranes on its fetal surface. Circumvallate placenta is a placental...
Placenta accreta occurs when all or part of the placenta attaches abnormally to the myometrium (the muscular layer of the uterine wall). Three grades of...
Placental abruption is when the placenta separates early from the uterus, in other words separates before childbirth. It occurs most commonly around 25...
Placenta cake is a dish from ancient Greece and Rome consisting of many dough layers interspersed with a mixture of cheese and honey and flavored with...
umbilical cord uncut after childbirth so that the baby is left attached to the placenta until the cord naturally separates at the umbilicus. This usually occurs...
A choriovitelline placenta is a placenta formed by the yolk sac and chorion. In a choriovitelline placenta, the yolk sac fuses with the chorion and, subsequently...
Retained placenta is a condition in which all or part of the placenta or membranes remain in the uterus during the third stage of labour. Retained placenta can...
when the placenta comes out of the birth canal after childbirth. The period from just after the baby is expelled until just after the placenta is expelled...
Placentation refers to the formation, type and structure, or arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases...
The placenta of humans, and certain other mammals contains structures known as cotyledons, which transmit fetal blood and allow exchange of oxygen and...
The placenta is an organ which links the fetus to the mother in mammals for the transfer of oxygen and nutrients to the fetus and fetal waste products...
umbilicalis) is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord is physiologically and...
ultrasound, or level 2 ultrasound, evaluates anatomic structures of the fetus, placenta, and maternal pelvic organs. This scan is an important and common component...
traditional placenta cake (known as "koptoplakous", κοπτοπλακοῦς), a dish similar to baklava, was consumed. The earliest known detailed recipe for placenta, from...
Arachnoides placenta is a species of sea urchin of the family Clypeasteridae. Their armour is covered with spines. It is placed in the genus Arachnoides...
involves the delivery of the neonate, as well as the placenta and fetal membranes. The placenta is a critical organ that develops in the maternal uterus...
haemorrhaging. There are 4 degrees of antepartum haemorrhaging: Placenta praevia refers to when the placenta of a growing foetus is attached abnormally low within...
Human placentophagy, or consumption of the placenta, is defined as "the ingestion of a human placenta postpartum, at any time, by any person, either in...
The windowpane oyster (Placuna placenta) is a bivalve marine mollusk in the family of Placunidae. They are edible, but valued more for their shells (and...
different before and after birth. The fetal circulation is composed of the placenta, umbilical blood vessels encapsulated by the umbilical cord, heart and...
the placenta. An artificial uterus may include components of equivalent function. Methods have been considered to connect an artificial placenta and other...
maternal part of the placenta and remains for the duration of the pregnancy. After birth the decidua is shed together with the placenta. The part of the decidua...
Placental site trophoblastic tumor is a form of gestational trophoblastic disease, which is thought to arise from intermediate trophoblast. The tumor may...
Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins (see multiple birth), these are...
They provide nutrients to the embryo and develop into a large part of the placenta. They form during the first stage of pregnancy and are the first cells...
Global Information
