corpus luteum A 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 PHYSIOLOGY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |