Periods (Menstruation)

One thing girls begin to experience is periods. Girls take care of their periods by wearing sanitary pads or putting tampons in their vaginas. Girls experience periods because they can have babies, unlike boys, who produce sperm in their testicles.

Periods, also called menstruation, happen when blood and a girl's egg leave the girl's body through her vagina if a sperm cell has not reached her egg through sex. It begins when an egg moves from one of two ovaries, through one of the girl's two fallopian tubes, to her uterus. Before the egg reaches the uterus, the uterus grows a layer of blood and tissue. If the girl has had sex and a sperm cell has reached her egg, she will become pregnant and have a baby, which forms in her uterus. If a sperm cell has not reached her egg, she will have her period, and the blood and egg leave through her vagina. Then the process repeats about once a month. You can't tell if a girl is on her period by looking at her.

Girls experience emotional changes and can sometimes feel much more strongly than boys. Girls can have worse mood swings about 7 days before their periods, called Premenstrual Syndrome (PMS). Girls can feel down during this time.

Boys gain more muscle during puberty, and girls gain more body fat.