6.6 – Reproduction
6.6.1 – Draw and label diagrams of the adult male and female reproductive systems
6.6.2 – Outline the role of hormones in the menstrual cycle, including FSH (follicle-stimulating hormone), LH (luteinising hormone), oestrogen and progesterone
Follicle Stimulating Hormone (FSH) – Released during days 5-13 from the pituitary gland. This stimulates the maturation of a follicle in the ovary. Also stimulates the secretion of oestrogen.
Luteinising Hormone (LH) – Released on day 14 to bring about ovulation, when the secondary oocyte detaches from the follicle wall, and the Graafian follicle to turn into the corpus luteum, which produces progesterone. Also causes less oestrogen to be secreted and more progesterone.
Oestrogen – Also released during days 5-13, reaching its peak levels around days 13-14, when it stimulates the release of LH. It causes the repair of the uterine tissue.
Progesterone – Released from the corpus luteum and causes the uterine wall to thicken and increases the blood supply, ready for implantation of a fertilised ovum. It inhibits the production of FSH so that no more follicles will mature in the ovary, as well as reducing oestrogen concentration. It will eventually inhibit LH and the activity of the corpus luteum.
6.6.3 – Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and thickening of the endometrium
6.6.4 – List three roles of testosterone in males
Pre-natal development of male genitalia – During gestation, the testes will secrete testosterone to stimulate the development of the male genitalia in the foetus, including the penis.
Development of secondary sexual characteristics – When the male reaches puberty, the testosterone levels will rise to cause the development of secondary sexual characteristics. These include pubic hair, an enlarged penis and growth of skeletal muscles.
Maintenance of sex drive – When the male reaches adulthood, their sex drive is maintained by testosterone. This instinct is important for encouraging them to have sexual intercourse to pass on their genes to offspring.
6.6.5 – Outline the process of in vitro fertilisation (IVF)
- A drug is injected daily for three weeks to stop the normal menstrual cycle
- The woman is given large daily doses of FSH for 10-12 days to stimulate the release of multiple follicles in the ovary
- HCG is then injected 36 hours before the ova are collected to mature them and make them loose in the follicle.
- Semen is collected from the male, which are processed to concentrate the healthiest ones
- The ova are extracted from the follicle using a device that is inserted through the wall of the vagina
- The ova are mixed with sperm in individual dishes overnight in an incubator
- The dishes are checked to see if fertilisation has occurred
- Two or three embryos are selected and placed in the uterus using a long plastic tube
- A pregnancy test is performed about 12 days later to see if any embryos implanted
- Two weeks later, scans are done to ensure that the pregnancy is continuing normally, including a visibly beating heart.
6.6.6 – Discuss the ethical issues associated with IVF