puberty and the menstrual cycle

• hormones promote sexual characteristics at puberty
• in males, the main reproductive hormone is testosterone, which is produced in the testes
• in females, the main reproductive hormone is oestrogen, which is produced by the ovaries
• testosterone promotes secondary male characteristics to develops, as well as the production of sperm
• oestrogen promotes secondary female characteristics to develop, as well as being involved in the menstrual cycle
• there are four stages in menstruation
• stage 1 menstruation: day 1, the uterus lining breaks down for about four days
• stage 2 menstrual cycle: the uterus lining builds up again, from day 4 to 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg
• stage 3 menstrual cycle - an egg develops and is released from the ovary at day 14, a process called ovulation
• stage 4 menstrual cycle - the way is maintained for 14 days until day 28, if no fertilised egg lands on the uterus wall by day 28, the spongy lining begins breaking down and the whole cycle starts again
• the menstrual cycle is controlled by four hormones: FSH (follicule-stimulating hormone) ; oestrogen ; LH (luteinising hormone) ; progesterone
• FSH is produced in the pituitary gland, it causes an egg to mature and stimulates the ovaries to produce oestrogen
• oestrogen is produced in the ovaries, it causes the lining of the uterus to grow and stimulates the release of LH and inhibits the release of FSH
• LH is produced by the pituitary gland and stimulates the release of an egg at day 14
• progesterone is produced in the ovaries and maintains the the lining of the uterus during the second half of the cycle, when progesterone levels fall, the lining of the uterus breaks down. it also inhibits the release of LH and FSH