Chapter 10- Human Growth and Development

10.1 Growth and puberty

The rate of growth is fastest as a baby, then slows down and steadies until puberty.
The changes ( in body shape, growth, voices, hair, sperm production-boys, and starting menstruation- girls) that happen during puberty are controlled by the sex hormones oestrogen and testosterone
Puberty starts when the pituitary gland is stimulated by the hypothalamus to release the hormones FSH and LH. These travel to testes/ovaries which start to secrete testosterone/oestrogen and cause puberty to start
The menstrual cycle lasts approximately 28 days, and ovulation occurs in the middle of the cycle
Because the cycle is controlled by hormones, the hormone oestrogen in a contraceptive pill can stop the release of an egg

1 of 2

There are4 main hormones controlling the menstrual cycle-
FSH (Follicle Stimulating Hormone) is produced by the pituitary gland and it stimulates follicles (egg-containing sacs) to grow and to produce oestrogen
LH (Luteinising Hormone) is produced by the pituitary gland and stimulates the release of an egg from a follicle and the development of corpus luteum, formed by follicle cells after ovulation
Oestrogen is produced by ovaries and causes the uterus lining to build up before ovulation
Progesterone is produced by corpus luteum in ovaries after ovulation and maintains the uterus lining for a fertilised egg
Rising oestrogen levels stimulate the release of LH, which stimulates ovulation and progesterone release.
If the egg is fertilised, it travels down the oviduct and embeds in the uterus lining. Oestrogen and progesterone continue to maintain the lining until 12 weeks
If the egg doesn't implant, oestrogen and progesterone are not produced (and corpus luteum degenerates), and the uterus lining breaks down

2 of 2