<prompt> What is a placental cotyledon:All branches from one stem villiArea supplied by one spiral aeryQuaer of placentaArea drained by one terminal villi  <response>: Functional unit of the placenta is called a fetal cotyledon or placentome,which is derived from a major primary stem villus. These stem villi pass down through the intervillous space to anchor onto the basal plate.About 60 stem villi persist in human placenta. Thus each cotyledontotalling 15-29 contains 3-4 major stem villi. Reference : Dutta Textbook of Obstetrics th edition page no 31 