When the ripe follicle ruptures (ovulation) and the oocyte is discharged from it, its walls collapse and its cavity is filled with blood and yellowish cells. As a result the yellow body (corpus luteum) is formed. The oocyte develops into a mature cell, after ovulation, in the uterine tube. When pregnancy occurs,  the corpus luteum increases in size and transforms into a large structure about 1 cm in diameter, corpus lucteum verum s. graviditatis, whose traces may persist for years; , the corpus luteum atrophies, loses its yellow colour and is now called the white body (corpus albicans). icd 10 training will teach all these.