© Oxford University Press Coming full circle Changes during puberty Boys Penis develops Voice deepens Facial hair grows Sperm production starts Both Hair grows on sex organs Spots appear Notice the opposite sex more Armpit hair grows Growth spurt Hair grows on legs Girls Breasts develop Periods start Hips widen

© Oxford University Press 2008 The menstrual cycle One of the changes that happens to girls during puberty is that their periods start. This is called the ‘menstrual cycle’ because it follows a pattern that repeats every 28 days. It happens because a girl’s body is preparing itself to receive a fertilised egg. 2.6 Coming full circle

© Oxford University Press 2008 The menstrual cycle 2.6 Coming full circle