corpus luteum A mass of yellow tissue that remains after ovulation when a mature Graafian follicle ruptures from the ovary of a mammal. It is formed by ingrowth of the follicle wall as a result of the action of luteinizing hormone (which in turn requires the presence of prolactin from the pituitary). If ovulation does not result in fertilization, then the corpus luteum quickly degenerates. If fertilization occurs, then the corpus luteum persists and continues to secrete luteal tissue during part or all of pregnancy.

corpus luteum (yellow body) The yellowish mass of tissue that forms from the granulosa cells in the cavity of a Graafian follicle in the ovary of a mammal after the release of the egg cell. It secretes the hormone progesterone. Some species of sharks, reptiles, and birds have similar structures in their ovaries but the function of these is less well understood.