Corpus luteum

A temporary structure in the ovary that arises after an egg is released from the follicle (ovulation). It secretes estrogen and progesterone. If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays – this triggers the shedding of the endometrium (menstruation). If fertilization does occur, the corpus luteum continues secreting progesterone to support implantation of the embryo in the endometrium.