The follicular phase of a woman's period begins on which day?

The follicular phase of a woman's menstrual cycle begins on the first day of menstruation. This phase is characterized by the growth and maturation of ovarian follicles, which are stimulated by follicle-stimulating hormone (FSH) released by the pituitary gland. The first day of the menstrual period marks the start of the cycle and signals the shedding of the uterine lining, indicating that a new cycle has commenced. As the follicles develop, one is typically selected to mature fully and be released during ovulation, which occurs later in the cycle. Thus, identifying the first day of menstruation as the beginning of the follicular phase is crucial for understanding the overall timing and events that occur in the menstrual cycle.