When does the follicular phase of the menstrual cycle begin?

The follicular phase of the menstrual cycle begins on the first day of menstruation, which is characterized by the shedding of the uterine lining. This phase is marked by the development of ovarian follicles and is regulated by the secretion of hormones from the pituitary gland, particularly follicle-stimulating hormone (FSH).

Starting from the onset of menstruation allows for a clear definition of the cycle's phases, establishing a baseline for subsequent hormonal changes leading to ovulation. During the follicular phase, the follicles develop and prepare for potential ovulation, which typically occurs around the middle of the cycle. Understanding the timing of this phase is crucial for recognizing how hormonal fluctuations influence fertility and menstrual health.

The other options do not accurately represent the beginning of the follicular phase; they refer to points in the cycle that occur after menstruation has started or does not align with the established phases of the menstrual cycle.