corpus luteumA mass of yellow tissue formed in the Graafian follicle in the ovary after the ovum (egg cell) is released. If the ovum is fertilized, the corpus luteum secretes progesterone, a hormone needed to prepare the uterus for pregnancy. If the ovum is not fertilized, the corpus luteum becomes inactive. Related category• ANATOMY AND PHYSIOLOGYAlso on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |