Biology of Controlling Fertility

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

2. 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

3. Physiology & Health Learning Intentions KEY AREA 3 – The Biology of Controlling Fertility • Infertility Treatments & Contraception (Biology of Fertility) • Treatments for infertility • Physical & chemical methods of contraception

4. 3a) The biology of controlling fertility Knowledge of the biology of fertilisation is used to help:- Design treatments for infertility Devise methods for contraception

5. 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 in the testes Cyclical fertile (FEMALES) The pituitary and ovarian hormones cause there to be a small window of fertility (2days) which occurs immediately after ovulation

6. 3a) Calculation of the Female Fertile Period Calculation of female fertile period can be indicated by:- Temperature Rise After the LH surge triggers ovulation, the women’s body temperature rises by about 0.5˚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 3rd 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

7. 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 prevent negative feedback of oestrogen on FSH secretion during the luteal phase • Drugs that mimic the normal action of FSH and LH • they can bring about “super-ovulation” which can lead to multiple births (e.g. twins, triplets) or can be used to collect ova for in vitro fertilisation (IVF) programmes

8. 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

9. 3d) Intracytoplasmic sperm injection (ICSI) The ICSI procedure involves drawing the head of a healthy sperm into a syringe needle and then injecting it directly into an egg to bring about fertilisation. This procedure is useful if the mature sperm are defective or very low in number. 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

10. 3e) Treatments for Infertility- In vitro fertilisation (IVF) IVF treatment is used to solve the problem of infertility caused by a blockage of the oviducts “In vitro” fertilisation means fertilisation occurring outside the body in a culture dish Steps in IVF 1. Woman given hormonal treatment to stimulate “super ovulation” 2. Surgery to remove several eggs from ovary 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

11. 3f) Treatments for Infertility In vitro fertilisation (IVF)

12. 3g) Pre-implantation screening and genetic diagnosis Before 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 single gene disorders and chromosomal abnormalities (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

13. 3h) 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:- - Barriers (physically block to ability of sperm to reach an ovum: 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

14. 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 mimic negative feedback control:- FSH and LH by the pituitary gland is inhibited Follicle maturation is inhibited Ovulation fails to occur Progesterone-only pill Mini-pills, Injection, Implants, Contain Synthetic Progesterone to thicken the cervical mucus to reduce sperm access to the uterus 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 ovulation or implantation. 3i) Contraception - Chemical methods

15. Physiology & Health Questions KEY AREA 3 – The Biology of Controlling Fertility • Testing Your Knowledge 1 Page 139 Q’s 1-4 2. Quick Quiz