Final answer:
The luteum develops as LH is at its highest, then matures as LH stays constant. The surge of LH stimulates a change in the granulosa and theca cells, transforming the collapsed follicle into the corpus luteum. The corpus luteum produces progesterone for pregnancy.
Step-by-step explanation:
The luteum develops as LH is at its highest, then matures as LH stays constant. After ovulation, the ovarian cycle enters its luteal phase and the menstrual cycle enters its secretory phase. The surge of LH stimulates a change in the granulosa and theca cells that remain in the follicle after the oocyte has been ovulated, transforming the collapsed follicle into a new structure called the corpus luteum. The luteinized granulosa and theca cells of the corpus luteum produce large amounts of the hormone progesterone, which is critical for the establishment and maintenance of pregnancy.