During which phase does menstrual flow occur?

The menstrual flow occurs during the menstrual phase, which is the first phase of the menstrual cycle. This phase typically lasts from about three to seven days and involves the shedding of the uterine lining (endometrium) when a fertilized egg does not implant. The decline in hormones, particularly estrogen and progesterone, triggers this phase, leading to the onset of menstruation.

In contrast, the other phases—ovulatory, luteal, and follicular—are characterized by different hormonal activities and physiological changes that prepare the body for potential pregnancy but do not involve menstrual flow itself. Understanding the timing and hormonal regulation of these phases is crucial for comprehending the menstrual cycle's overall function.