HHB physiology and health - the biology of controlling fertility

compare fertility periods in males and females

men show continuous fertility while women show cyclical fertility

explain why females have cyclical fertility and males have continuous fertility

women show cyclical fertility as they have a fertile period, women are only fertile for a few days each menstrual cycle

while men show continuous fertility as they are always able to produce sperm in their testes

describe the physiological changes which indicate a woman is in her fertile period

during a woman's fertile period their body temperature rises by around 0.5 °C after ovulation and her cervical mucus becomes thin and watery

give examples of causes of infertility in both males and females

causes of infertility in males are low sperm count, abnormal sperm with tail or head defects and low motility (sperm cannot swim efficiently)

causes of infertility in females are a hormonal imbalance which can cause a failure to ovulate or implantation failure and blocked oviducts

describe the process of artificial insemination

artificial insemination is when sperm are injected/introduced with a syringe into the uterus through the cervix

several samples of semen can be collected over a period of time to create a concentrated sample which can then be used for insemination

suggest when artificial insemination should be used

this is useful when the male has a low sperm count

explain why donor sperm are sometimes used for artificial insemination

if a partner is sterile, a donor may be used to provide semen for artificial insemination

describe how to stimulate ovulation using drugs

ovulation can be stimulated by drugs that prevent the negative feedback effect of oestrogen on the release of FSH which encourages more follicles to develop

or drugs which copy (mimic) the action of FSH and LH, causing super ovulation which allows multiple ova to be collected for in vitro fertilisation (IVF) programmes, this can result in multiple births

describe how ova are collected for IVF programmes

during IVF, ova are surgically removed from ovaries after hormone stimulation

describe the process of IVF

IVF involves fertilisation outside the women's body, ova are surgically removed from ovaries after hormone stimulation
and then are mixed with sperm in a culture dish to be fertilised

once fertilised, the fertilised eggs are incubated until they have formed at least eight cells (early embryo) these are then transferred to the uterus for implantation

suggest when IVF should be used

IVF are used when males have a low sperm count, there are problems with ovulation and the oviducts of the female are blocked

describe the process of ICSI

during ICSI, the head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation, this is a form of IVF

suggest when ICSI should be used

ICSI is a form of IVF which is used if mature sperm are defective or very low in number

explain why PGD is available to some couples

PGD can be used to identify single gene disorders and chromosomal abnormalities as this can prevent inherited conditions from being passed on

give examples of physical methods of contraception and describe how they prevent pregnancy

barrier methods such as condoms and diaphragm prevent fertilisation, intra uterine devices (IUDs) prevent implantation of the blastocyst (early embryo) and sterilisation prevents fertilisation

describe how the oral contraceptive pill, progesterone only and morning after pill prevent pregnancy

the oral contraceptive pill contains both oestrogen and progesterone, higher levels of these hormones will mimic the natural negative feedback effect and will prevent the release of FSH and LH from the pituitary therefore preventing the development of follicles and ovulation

the progesterone-only (mini) pill causes thickening of the cervical mucus preventing sperm entering the uterus

the emergency hormonal contraceptive pill (morning after pill) prevents or delays ovulation to avoid fertilisation