What structure in the ovary becomes a copus luteum?

The structure in the ovary that becomes a corpus luteum is the Graafian follicle, specifically after ovulation. Once the mature follicle releases an egg during ovulation, the remaining follicular cells transform into the corpus luteum. This structure produces hormones, primarily progesterone, which are critical for maintaining the uterine lining in preparation for a potential pregnancy. If fertilization does not occur, the corpus luteum eventually degenerates into a corpus albicans.