n. pl. pla·cen·tas or pla·cen·tae (-tē)
a. A membranous vascular organ that develops in female eutherian 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.
b. A similar organ in marsupial mammals, consisting of a yolk sac attached to the uterine wall.
c. An organ with similar functions in some nonmammalian animals, such as certain sharks and reptiles.
2. Botany The part within the ovary of a flowering plant to which the ovules are attached.
[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 the Appendix of Indo-European roots.]
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