Higher Human Biology Unit 2 Physiology & Health KEY AREA 3: Biology of Controlling Fertility

Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : - Key Area 1 – Reproductive Organs Key Area 2 –Hormonal Control of Reproduction Key Area 3 – Biology of Controlling Fertility Key Area 4 – Ante- and Postnatal Screening Key Area 5 – Structure and Function of Arteries, Capillaries and Veins Key Area 6 – Structure and Function of the heart Key Area 7 – Pathology of Cardiovascular Disease (CVD) Key Area 8 – Blood Glucose Levels and Obesity

Physiology & Health Learning Intentions KEY AREA 3 – The Biology of Controlling Fertility a)Infertility Treatments & Contraception (Biology of Fertility) b)Fertile Periods c)Treatments for Infertility d)Contraception

3a) The biology of controlling fertility Knowledge of the biology of fertilisation is used to help:- Design treatments for infertility Devise methods for contraception

3a) Fertile periods – MEN v WOMEN! Men are CONTINUOUSLY FERTILE whereas Women are CYCLICAL FERTILE Continuously fertile (MALES) This is due to the fact that the negative feedback control of testosterone maintains a relatively constant level of pituitary hormones FSH and ICSH in the bloodstream so sperm are constantly being made Cyclical fertile (FEMALES) The pituitary and ovarian hormones cause there to be a small period of fertility (2days) which occurs immediately after ovulation

3a) Calculation of the Female Fertile Period Calculation of female fertile period can be indicated by:- Temperature Rise One day after the LH surge triggers ovulation, the women’s body temperature rises by about ˚C due to progesterone action and the temperature remains elevated for the duration of the luteal phase The fertile period lasts for 1-2 days After the 3 rd day of elevated temperatures, the infertile period is resumed and the unfertilised ovum disintegrates Thin, Watery Cervical Mucus During the fertile period, cervical mucus is thin and watery to allow sperm easier access to the oviducts After ovulation, the mucus increase in viscosity (due to progesterone), showing the infertile period is resumed

3b) Treatments for Infertility – Stimulating Ovulation Stimulating ovulation A woman may fail to ovulate because of an underlying factor e.g. failure of the pituitary gland to secrete FSH or LH In these cases ovulation can be successfully stimulated by using:- Drugs that mimic the normal action of FSH and LH Drugs that prevent negative feedback of oestrogen on FSH secretion during the luteal phase Ovulation stimulating drugs are often so effective, they bring about “super-ovulation” which can lead to multiple births (e.g. twins, triplets)

3c) Treatments for Infertility – Artificial Insemination Naturally, during sexual intercourse, semen is introduced into the female reproductive system If a man has a low sperm count, artificial insemination can be used. Artificial insemination is the introduction of semen into the female reproductive tract by some other means than sexual intercourse Artificial insemination involves collecting several samples of the man’s semen and freezing it until required. When ready, the semen are defrosted and released into the female’s cervix during her fertile period. Semen from a donor can also be used in this process if the man is sterile

3d) Treatments for Infertility- In vitro fertilisation (IVF) “In vitro” fertilisation means fertilisation occurring outside the body in a culture dish IVF treatment is used to solve the problem of infertility caused by a blockage of the oviducts Steps in IVF 1. Woman given hormonal treatment to stimulate “super ovulation” 2. Surgery to remove several eggs 3. Eggs mixed with sperm in a culture dish of nutrient medium to allow fertilisation to occur OR a sperm may be injected directly into an egg(ICSI) 4. Fertilised eggs are incubated in nutrient medium for 2-3days to allow cell division to occur so they form embryos (each composed of 8 or more cells) 5. Two or Three of the embryos are chosen and then inserted into the mothers uterus (which is ready for implantation) 6. Remaining embryos are frozen and stored in case a second attempt at implantation is required

3d) Treatments for Infertility- In vitro fertilisation (IVF) Intracytoplasmic sperm injection (ICSI) procedure involves drawing healthy sperm into a syringe needle and then injecting it directly into an egg to bring about fertilisation. During the procedure the egg is held in place by a holding tool Eggs from a donor can also be used in this process if the female’s egg’s are non-viable

3d) Treatments for Infertility In vitro fertilisation (IVF)

3e) Pre-implantation screening and genetic diagnosis Before stage 5 of IVF, one or two cells may be removed and tested for genetic abnormalities. The test may be one of the following:- 1. Pre-implantation Genetic Screening (PGS) A non-specific approach that checks the embryo for single gene disorders and common chromosomal abnormalities in general (e.g. Down Syndrome) 2. Pre-implantation Genetic Diagnosis (PGD) A specific- approach to check for a known chromosomal or gene defect (e.g. Tay Sach’s) PGS and PGD are used to help scientists identify embryos which should and should not be allowed to become implanted in the mother’s endometrium Ethical Debate Some people strongly feel that PGS and PGD help couples to have children who may have opted to be childless if they were high risk for specific abnormalities. These people also believe that reducing genetic disorders in society is beneficial. Other people believe that it is morally wrong to interfere with conception and humans should not be able to select “designer” children!

3f) Contraception – Physical Methods Contraception is the intentional prevention of conception or pregnancy by natural or artificial means Physical methods which block the ability of sperm to reach an ovum include:- Condom Diaphragm Cervical cap Intra-uterine device (IUD) Sterilisation procedures In men, a vasectomy involved cutting and tying the two sperm ducts. This prevents sperm being released during sexual activity In women, a tubal ligation involved cutting and tying the two oviducts. This prevents eggs meeting sperm and reaching the uterus Textbook Page 136

3g) Contraception - Chemical methods Pills containing a combination of hormones Oral contraceptive pills normally contain synthetic progesterone combined with synthetic oestrogen This procedure makes the concentration of progesterone and oestrogen increase in the bloodstream and bring about the following negative feedback control:- FSH and LH by the pituitary gland is inhibited Follicle maturation is inhibited Ovulation fails to occur Morning after pills Emergency hormonal contraception which contain high doses of progesterone and oestrogen, and are taken by a women who has had unprotected sexual intercourse, to prevent implantation. Synthetic Progesterone Mini-pills, Injection, Implants, Contain Synthetic Progesterone to thicken the cervical mucus to reduce sperm access to the uterus

Physiology & Health Questions KEY AREA 3 – The Biology of Controlling Fertility 1.Testing Your Knowledge 1Page 139 Q’s Quick Quiz