The average menstrual cycle is characterized by the release of what?

The average menstrual cycle is characterized by the release of an egg, also known as ovulation. During the menstrual cycle, follicles in the ovaries mature, and typically one follicle will release a mature egg around the midpoint of the cycle. This event is critical for reproduction, as the released egg can be fertilized by sperm, which may lead to the development of a zygote if fertilization occurs.

The menstrual cycle also involves preparation within the uterus for potential implantation of a fertilized egg. If fertilization does not take place, the cycle concludes with menstruation, where the unfertilized egg and uterine lining are shed.

Thus, the correct answer highlights the importance of the egg in the cycle, distinguishing it from the other terms. Sperm, zygotes, and follicles have different roles: sperm are involved in fertilization, zygotes are the result of fertilization, and follicles are structures that contain the eggs but are not released themselves during ovulation.