Corpus albicans. Light micrograph of a section through an ovary showing a corpus albicans (centre). Each menstrual cycle one egg (ovum) reaches maturity and develops into a Graafian follicle. The Graafian follicle releases the egg at ovulation and then develops into a corpus luteum, which secretes progesterone to build up the lining of the uterus, ready for a fertilised egg. If there is no fertilised egg after 12 days the corpus luteum stops secreting and degenerates into a corpus albicans.