Corpus luteum. Light micrograph of a section through the corpus luteum of an ovary. The corpus luteum is the tissue formed from a mature ovarian follicle after the follicle has released its oocyte during ovulation. The cells at left developed from follicular granulosa cells, while the cells at right developed from follicular theca interna cells. The corpus luteum secretes progesterone, androgens, oestrogens and inhibin, which together serve to inhibit follicle development while preparing the uterus lining for pregnancy. Magnification: x300 when printed at 10 centimetres wide.