Puberty and the menstrual cycle, the four hormones that control it, methods of contraception, and fertility treatment including IVF.
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1.What happens during puberty?
Reproductive hormones cause secondary sex characteristics to develop, and gametes begin to be produced.
2.Which hormone causes male secondary sex characteristics?
Testosterone, produced by the testes.
3.What else does testosterone do?
It stimulates sperm production.
4.Which hormone is the main female reproductive hormone?
Oestrogen, produced by the ovaries.
5.What is ovulation?
The release of a mature egg from the ovary, roughly every 28 days.
6.Name the four hormones that control the menstrual cycle.
FSH, LH, oestrogen and progesterone.
7.What does FSH do, and where is it made?
Made in the pituitary gland. It causes an egg to mature in the ovary.
8.What does LH do, and where is it made?
Made in the pituitary gland. It stimulates the release of the egg, which is ovulation.
9.What does oestrogen do in the cycle?
It is made in the ovaries and causes the lining of the uterus to grow and thicken. It also inhibits FSH and stimulates LH.
10.What does progesterone do?
It maintains the lining of the uterus during the second half of the cycle, and inhibits both FSH and LH.
11.What happens if the egg is not fertilised?
Progesterone levels fall, the uterus lining breaks down, and menstruation happens.
12.Give three hormonal methods of contraception.
The contraceptive pill, an implant, an injection, a skin patch, or an intrauterine device that releases a hormone.
13.How does the oral contraceptive pill work?
It contains hormones that inhibit FSH production, so no eggs mature.
14.How do implants and injections work?
They slowly release progesterone, which inhibits the maturation and release of eggs, sometimes for years.
15.Give three non-hormonal methods of contraception.
Barrier methods such as condoms or a diaphragm, a copper intrauterine device, spermicides, abstinence, and surgical sterilisation.
16.Which method of contraception also protects against sexually transmitted infection?
Barrier methods, in particular condoms.
17.Give an advantage and a disadvantage of hormonal contraception.
It is very effective at preventing pregnancy, but it can have side effects and gives no protection against sexually transmitted infection.
18.How can hormones be used to treat infertility?
FSH and LH can be given as a fertility drug to stimulate eggs to mature and be released.
19.Give a disadvantage of fertility drugs.
They do not always work, and they can result in multiple births, which carry risks for the mother and the babies.
20.What does IVF stand for?
In vitro fertilisation.
21.Describe the stages of IVF.
The mother is given FSH and LH to mature several eggs, the eggs are collected and fertilised by sperm in the laboratory, the fertilised eggs develop into embryos, and one or two are inserted into the uterus.
22.Give two disadvantages of IVF.
It is emotionally and physically stressful, the success rate is not high, and it can lead to multiple births which are risky.
23.Why is IVF controversial for some people?
Spare embryos are often destroyed, and some people object to this on ethical or religious grounds.
24.Why is the success rate of IVF an important consideration?
The procedure is expensive and demanding, so a low chance of success has to be weighed against that cost.
25.How does microscopy help IVF?
Modern microscope techniques allow a single sperm to be injected directly into an egg, and let embryologists select healthy embryos.
26.Why does oestrogen inhibit FSH?
It is negative feedback. Once an egg is maturing, stopping FSH prevents further eggs from developing at the same time.
27.Roughly how long is the menstrual cycle and when does ovulation happen?
About 28 days, with ovulation around day 14.
28.Why might a doctor measure hormone levels to investigate infertility?
Low levels of FSH or LH would explain why eggs are not maturing or being released, and can be treated with fertility drugs.
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