" A Fetus - Umbilical Cord - Placenta", 1988 Kiki Smith (1954) Montreal Museum of Fine Arts, Quebec, Montreal, Canada.
The term "placenta" derives from its similarity to a cottage cheese cake. In this image, the spiral of the cord is clock-wise (which decreases the possibility of bending and clamping of arterial and venous flow). The ancients compared the brittleness of the placenta with cottage cheese (lack of elasticity) - during birth, as the uterus contracts, the placenta detaches.
The placenta is a fetal organ - rarely the placenta survives in the absence of a fetus (think of triploidy - 69 chromosomes or 3 times 23).
NOTE: As a vital organ, the term "placenta" conveys a plethora of related notions including placid, ..., pleasure (see related terms).