2.2 Biological Control Of Fertility Flashcards
What factors can affect fertility?
Weight, stress, disease and pollutants (e.g. Cigarette smoke)
What are the two types of fertility?
Continuous fertility and cyclical fertility
Why do men have continuous fertility
Men have potential to become a father from onset of puberty due to the negative feedback control of testosterone
Describe the negative feedback effect of testosterone
It maintains a constant level of the pituitary hormones FSH & ICSH in the bloodstream, resulting in the steady release of testosterone
Why is fertility in women described as cyclical
Women produce eggs from puberty onwards until menopause. Menopause is when ova are no longer released from the ovaries and menstruation no longer occurs.
What age does menopause occur from
45-55
When can a woman fall pregnant
A few limited days either side of ovulation
How long does the fertility period in women last for
1-2 days
What indicators in the rhythm method are used when calculating a woman’s fertile period
Body temperature rise of 0.5’C and a change in the consistency of the cervical mucus
What is the state of the cervical mucus when a woman is infertile
Thick and sticky
What is the state of the cervical mucus when a woman is fertile and why
The mucus is thinner, slippery and stretchy which allows easy access for the sperm to the female reproductive system
Why causes the cervical mucus to become thinner, slippery and stretchy when a woman is fertile
The increasing oestrogen levels in the follicular phase
What advances have helped treatment of infertility
Modern medicine advances
What treatments are there for infertility
Stimulating ovulation, artificial insemination, in vitro fertilisation (IVF) and intra cytoplasmic spent injection
What drugs are given to help stimulate ovulation
Drugs that mimic the negative feedback effect of oestrogen on FSH secretion. Drugs that mimic the normal action of FSH & LH
What can the drugs used for ovulation stimulation cause
Can cause ‘super ovulation’ resulting in multiple births or be used to collect ova for IVF
What is artificial insemination
The insertion of semen into the female reproductive tract by means other then sexual intercourse
What are the two situations of artificial insemination
Low sperm count - several samples of semen collected over a period of time and each preserved by freezing. Then they are defrosted and released together into the female reproductive tract at the fertile time. Donor sperm required - If a male is sterile then semen samples may be obtained from a donor
What is IVF
The solution to infertility in which it enables fertilisation to occur outside the body in a culture dish.
What can IVF be used in conjunction with and why
PGD - to identify any known single gene disorders or chromosomal abnormalities
Outline stage one of IVF
Woman is given hormonal treatment to stimulate multiple ovulation
Outline stage two of IVF
Surgical procedure to remove several ova from around the ovary using equipment similar to a syringe
Outline stage three of IVF
The eggs are mixed with sperm I’m a culture dish of nutrient medium to allow fertilisation to occur. Alternatively sperm would be injected into an egg at this point
Outline stage four of IVF
The fertilised eggs are incubated in the nutrient medium for 2-3 days to allow cell division to occur and form embryos each composed of 8 cells or more.
Outline stage five and six of IVF
Two or three of the embryos are chosen and then inserted into the uterus via the caging. The remaining embryos are then frozen and preserved incase required for second implantation
When does PGD occur
Before the embryo is inserted into the females uterus a sample of cells is collected from the embryo to test for known chromosomal abnormalities or gene defects
What are the ethical issues of PGD
It can offer some couples reassurance but some people think it is morally wrong to be selective in the process of conception
What are the long term effects of IVF on the mother
Women can suffer hyperstimulation of the ovaries. Too many eggs can be produced causing the ovaries to become swollen and sore. Women may have increased risk of uterine cancer
What are the long term effects of IVF on the children
Children conceived of IVF may have a lower body mass at birth. Children with low body mass are more like to suffer obesity, diabetes, heart conditions and hypertension later in life.
What is intra cytoplasmic sperm injection
The insertion of one sperm directly into an egg cell.
What is done to the sperm in ICSI
The sperm is immobilised by having its tail removed.
Describe the process of ICSI
The head of the sperm is drawn into a needle and injected directly into an egg cell to achieve fertilisation.
Why is ICSI commonly used
If sperm is defective or very low in number
Define contraception
The intentional prevention of conception or pregnancy by natural or artificial means
What is a natural contraception
Family planning - using the rhythm method to identify a woman’s fertile period then abstaining from sexual intercourse at that period of time
What are the two types of artificially contraception
Physical (barriers) and chemical
What is a physical method of contraception
Sterilisation as it blocks the ability of the sperm to access the egg. Vasectomy in men - cutting and tying of the sperm ducts. Tubal ligation in women - cutting and tying of the oviducts.
What are chemical contraceptives based on
Combinations of synthetic hormones that mimic negative feedback preventing the release of FSH/LH
What the the two types of contraceptive pill
Progesterone only pill and the morning after pill
Explain the progesterone only pill
Contains only synthetic progesterone and they cause the thickening of the cervical mucus which reduces the viability of the sperm and their access to the egg.
Describe the morning after pill
This is an emergency hormonal contraception pill. They contain higher doses of progesterone and oestrogen and prevent implantation from occurring by causing the endometrium to shed. Taken immediately after unprotected sexual intercourse and are effective up to 72 hours
