Definition of "placenta" [pla•cen•ta]

• 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. (noun)
• An organ with similar functions in some nonmammalian animals, such as certain sharks and reptiles. (noun)
• Botany The part within the ovary of a flowering plant to which the ovules are attached. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "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."