6.6 ReproductionMenstrual Cycle: - Hormones control the whole cycle- These levels will fluctuate in the blood (this is controlled by negative feed back mechanism)- Action of one hormone may inhibit the production of another

Hormones: - Two are produced by pituitary glands= Follicle Stimulating hormone (FSH) and luteinizing hormone (LH)- Two that are produced by the ovaries= oestrogen and progesterone

Testosterone – maintains sex drive, development of secondary sexual characteristic, prenatal development of male genetalia

Menstrual cycle starts when vagina starts bleeding

1) Several immature eggs will complete the stage of maturation= as this matures it is surrounded by layers of follicle cells (have a protective function)= known as a Graafian follicle2) One or two of the Graafian follicles will travel by the fallopian tube towards the uterus- Outer layer of follicle cells stay and develop into the Corpus LuteumMature egg and inner layer of follicle cells will leave to the uterus

FSH: - Being to rise during menstruation= stimulates maturing of Graafian follicle

LH: - Stimulates ovulation

Oestrogen: Rise after FSH= stimulates release of oestrogen from the ovaries= and these levels rise, they coincide in the repairs of the uterus lining (FSH blocks Oestrogen production= example of negative feedback)= Oestrogen stimulates LH

Progesterone= Low until ovulation= due to the Corpus Luteum (LH stimulates Progesterone)= high levels of progesterone maintain the uterus lining

Days 1-5: - FSH secretion goes up- Stimulates development of Graafian follicle in ovary- Stimulates ovary to produce oestrogen

Day 6-12: - Oestrogen secretion begins- Promotes repair of uterine lining- Stimulates production of LH from pituitary- Inhibits production of FSH

Stimulates release of oestrogen from the ovaries

Days 13-14 LH secretion peaks

- Stimulates ovulation (in presence of oestrogen) - Stimulates development of the corpus luteum - Stimulates production of progesterone

Days 15-24 Progesterone secretion increases

- Promotes thickening and growth of blood vessels in uterine lining- Inhibits production of FSH and LH

Days 25-28 LH secretion is inhibited

- As levels fall, c

Pregnant women don’t have their period during pregnancy because of the hormone hcG, which maintains the corpus luteum Takes over the role of LH so that the corpus luteum is sustained and progesterone levels are still high Corpus luteum can only be maintained for 3 months As the embryo increases in size needs more progesterone so the placenta starts producing progesterone First trimester is most dangerous for an embryo because the cross over period between corpus luteum and placenta switching in which one produces progesterone there could be a drop which could cause a miscarriage Corpus luteum disintegrates To increase fertility increase LH and FSH hormone (given as part of the IVF treatment) Contraceptives exploit these hormones, contain progesterone for females inhibit release of FSH so no follicle cells will mature Inhibit release of LH

Negative feedback mechanism

IVF treatmento FSH and LH are given to stimulate multiple egg releaseso Eggs are harvested – under an ultra sound the graafian follicle looks like a

dark swelling so easy to seeo Eggs are in a dish with nutrient media and incubated (this is IVF)o Father’s sperm is screened for quality i.e. number, damaged then it used to

fertilize the eggs in the disho After incubation viable fertilized blastocysts (ball of undifferentiated cells) are

selected and developed in to embryos Up to 2-3 embryos can be selected for implantation o 5 days after fertilisation the embryos are implanted Risk of multiple pregnancyo Mother can also be given progesterone during implantation to maintain uterus

liningo After a month pregnancy test is administered, if +ve pregnancy continues as

normalo If –ve woman must wait a few months before beginning the process again as

her body needs time to recover

Ethical considerations for IVFo The right to have children Improving medical technology makes it safer Some governments i.e. NHS in UK cover this cost Hope given to those who cannot conceive naturally Unused embryos can be stored and used later, donated or used as a source of

stem cellso Religious: playing God Interfering with nature or God Risk to the mother and fetuses if it results in a multiple pregnancy Expensive $60,000-$80,000 HKD – waste of money and waste of resources

could be used on medical care of diseases Emotional cost of failure, especially as mother has had high hormone dose Does termination of excess embryos count as ending a human life? Where is

the line drawn?

Ectopic pregnancyo Embryo or zygote implants in the fallopian tube instead of the uterus lining Must have emergency operation to remove it