: FSH travels to the ovaries, prompting several follicles to grow. Eventually, one "dominant" follicle emerges and begins producing high levels of estrogen .
To explain the physiology, you must start with the hormones.
Timing (28-day cycle): Day 1 = First day of menses.
Responds to GnRH by secreting Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH) .
Understanding Menstrual Cycle Physiology: A Comprehensive Guide