Biology of fertility control Higher Human Biology
Learning Intention Compare fertile periods in females and males
What is infertility? Infertility is the inability of a sexually active, non-contracepting couple to achieve pregnancy in one year.
The Biology of Controlling Fertility Infertility treatments and contraception are based on the biology of fertility. Fertility Males are continuously fertile due to a constant level of pituitary hormones (FSH and ICSH) Female fertility is cyclical
Female Fertility Females are fertile around 1-2 days after ovulating. A females fertile period can be calculated by factors like temperature and thickness of cervical mucus. Calculation of fertile period can be used when trying to conceive.
Infertility in Females Estimate 30-40% of Scots have fertility problems Failure to ovulate due to -hormonal imbalance -stress Blocked oviducts -Infections (STI s) -Fibroids -Spasms Implantation failure -Hormonal imbalance
Infertility in Males Low sperm count (<20 million sperm / ml), abnormal sperm, low motility Hormonal problems due to -Stress -Poor diet -Smoking, alcohol, drugs
Learning Intention Explain how ovulation can be stimulated
Female fertility Treatment A woman might fail to ovulate if she is not producing enough FSH or LH. To treat this, she can be given drugs that: Mimic the normal action of FSH and LH Prevent the negative feedback effect of oestrogen on FSH Sometimes this treatment can bring about superovulation which can lead to multiple births.
Treatments for Infertility Summary Ovulation stimulated by drugs that prevent the negative feedback effect of oestrogen on FSH secretion. Other ovulatory drugs mimic the action of FSH and LH. These drugs can cause super ovulation that can result in multiple births or be used to collect ova for in vitro fertilisation (IVF) programmes.
Learning Intention Explain how artificial insemination to overcome fertility issues Explain intracytoplasmic sperm injection is used to overcome fertility issues
Artificial Insemination The average sperm count in men is 20 to 150 million per millilitre of semen Low sperm count classified as fewer than 20 million sperm per millilitre of semen Artificial insemination is used to treat problems with sperm count Sperm are placed inside the uterus, near an oviduct using a catheter If male is sterile sperm from a donor can be used
Intracytoplasmic Sperm Injection ICSI can be used if a man has a low sperm count or if his mature sperm are defective in some way. It involves sperm being drawn up into a needle and then injected straight into the cytoplasm of the egg.
Artificial Insemination and ICSI Summary Several samples of semen are collected over a period of time. Artificial insemination is particularly useful where the male has a low sperm count. If a partner is sterile a donor may be used. (ICSI) If mature sperm are defective or very low in number ICSI can be used the head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.
Learning Intention Explain how in vitro fertilisation is used to overcome fertility issues.
IVF In vitro fertilisation (IVF) occurs outside the body. It can be used if a woman s oviduct is blocked. For this to happen, the sperm and the egg have to be removed.
IVF Hormonal treatment stimulates development of multiple follicles This stimulates multiple ovulation Eggs removed using a hollow needle
IVF Sperm collected and best selected Sperm & eggs combined in a dish containing nutrient medium Fertilised eggs incubated until they have formed at least 8 cells Healthiest embryos selected
IVF More hormonal treatment (progesterone) Scan to check thickness of endometrium 2 or 3 embryos transferred to uterus for implantation Any remaining embryos can be frozen in case a second attempt is required.
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Pre-implantation genetic screening This is not a specific approach, it checks the embryo for general gene disorders and common chromosomal abnormalities.
Pre-implantation genetic diagnosis This is a specific approach that is used to check for a known chromosomal or gene defect.
Ethics of IVF What do you think the ethical issues with IVF and genetic screening are? You are now going to be doctors and you will be given details on couples who have applied to have IVF. You have to decide which patient will be chosen to have the procedure.
Reason for infertility Possible treatment method Failure to ovulate Blocked oviduct Drugs that Mimic the normal action of FSH and LH or prevent the negative feedback effect of oestrogen on FSH IVF treatment Low sperm count Artificial Insemination Mature sperm are defective ICSI
IVF Summary Surgical removal of eggs from ovaries after hormone stimulation. Incubation of zygotes and uterine implantation. (The eggs are mixed with sperm in a culture dish. The fertilised eggs are incubated until they have formed at least eight cells and are then transferred to the uterus for implantation.) Pre-implantation genetic diagnosis (PGD). The use of IVF in conjunction with PGD to identify single gene disorders and chromosomal abnormalities.
Learning Intention Outline different methods of physical and chemical contraception.
Physical Contraception Physical methods of contraception are: The condom The diaphragm The cervical cap Intra-uterine devices (IUD) Sterilisation (vasectomy in men and tubal ligation in women) These methods are effective but not as successful as chemical methods.
Chemical Contraception Chemical contraception involves taking pills that contain specific hormones: The combined pill contains oestrogen and progesterone The morning-after pill also contains these hormones but a stronger dose The mini pill only contains progesterone The combined pill prevents ovulation while the mini pill causes thickening of the cervical lining to reduce viability of sperm. glow clip
Methods of Contraception