Placentation

Placentation
Placentation
	Placentation in the human resulting from cleavage at various gestational ages
Details
Identifiers
Latin	placentatio
MeSH	D010929
	Anatomical terminology

Placentation refers to the formation, type and structure, or arrangement of the placenta. The function of placentation is to transfer nutrients, respiratory gases, and water from maternal tissue to a growing embryo, and in some instances to remove waste from the embryo. Placentation is best known in live-bearing mammals (theria), but also occurs in some fish, reptiles, amphibians, a diversity of invertebrates, and flowering plants. In vertebrates, placentas have evolved more than 100 times independently, with the majority of these instances occurring in squamate reptiles.

The placenta can be defined as an organ formed by the sustained apposition or fusion of fetal membranes and parental tissue for physiological exchange.^[1] This definition is modified from the original Mossman (1937)^[2] definition, which constrained placentation in animals to only those instances where it occurred in the uterus.

^ Cite error: The named reference :0 was invoked but never defined (see the help page).
^ Mossman, H. Comparative Morphogenesis of the Fetal Membranes and Accessory Uterine Structures Vol. 26 (Carnegie Institution of Washington, 1937).

[:0-1] Cite error: The named reference :0 was invoked but never defined (see the help page).

[2] Mossman, H. Comparative Morphogenesis of the Fetal Membranes and Accessory Uterine Structures Vol. 26 (Carnegie Institution of Washington, 1937).

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