n.; pl. L. Placentæ E. Placentas [ L., a cake, Gr. &unr_; a flat cake, from &unr_; flat, fr. &unr_;, &unr_;, anything flat and broad. ] 1. (Anat.) The vascular appendage which connects the fetus with the parent, and is cast off in parturition with the afterbirth. [ 1913 Webster ]

☞ In most mammals the placenta is principally developed from the allantois and chorion, and tufts of vascular villi on its surface penetrate the blood vessels of the parental uterus, and thus establish a nutritive and excretory connection between the blood of the fetus and that of the parent, though the blood itself does not flow from one to the other. [ 1913 Webster ]

2. (Bot.) The part of a pistil or fruit to which the ovules or seeds are attached. [ 1913 Webster ]

a. 1. Of or pertaining to the placenta; having, or characterized by having, a placenta; as, a placental mammal. [ 1913 Webster ]

2. (Zool.) Of or pertaining to the Placentalia. [ 1913 Webster ]

n. (Zool.) One of the Placentalia. [ 1913 Webster ]

‖n. pl. [ NL. ] (Zool.) A division of Mammalia including those that have a placenta, or all the orders above the marsupials. [ 1913 Webster ]

a. Having reference to the placenta; as, the placentary system of classification. [ 1913 Webster ]

n. 1. (Anat.) The mode of formation of the placenta in different animals; as, the placentation of mammals. [ 1913 Webster ]

2. (Bot.) The mode in which the placenta is arranged or composed; as, axile placentation; parietal placentation. [ 1913 Webster ]