The upper two-thirds of the vagina refers to the portion of the vaginal canal that extends from the cervix to the vaginal opening. This area is lined with a mucous membrane that helps maintain moisture and provides protection. It plays a crucial role in sexual intercourse and childbirth, as it can expand and contract. This section of the vagina is also involved in the menstrual cycle, as it connects to the uterus, where menstrual blood flows during menstruation. The upper two-thirds contains various structures, including Bartholin's glands, which produce lubrication, enhancing comfort during sexual activity.