This 3D animation shows you the basics of the menstrual cycle. The menstrual cycle begins with menstruation. Once the bleeding stops, the uterine lining becomes thicker and begins to prepare for the possibility of a pregnancy. Somewhere around day 14, an egg is released from one of the ovaries and begins its journey down the fallopian tubes to the uterus. If sperm are present in the fallopian tube, fertilization can occur. If the egg is not fertilized, the egg breaks down and hormonal changes signal the uterus to prepare to shed its lining, bringing us back to day one of the menstrual cycle.



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