Biological Control of Fertility Flashcards
Give 4 examples of factors which can affect a person’s fertility?
weight
stress
disease
pollutants e.g. cigarette smoke
What are the 2 types of fertility?
Continuous
Cyclical
What do men have the potential to father?
a child from puberty onwards due to the negative feedback effect of testosterone
What does the negative feedback effect of testosterone maintain?
a constant level of the pituitary hormones FSH and ICSH in the bloodstream, resulting in the steady release of testosterone
What does the steady release of testosterone cause?
sperm to be continually produced in the testes , resulting in men being fertile throughout their lives.
When do women only release eggs?
from puberty until they reach the menopause
What is the menopause?
when ova are no longer released from the ovaries and menstruation no longer occurs.
In most women when does menopause occur?
45-55
When can a woman fall pregnant?
Each month there is only a limited number of days either side of ovulation
What does the interaction of the pituitary and ovarian hormones result in?
the period of fertility in females only lasting for 1-2/3-4 days
What is a woman’s fertility?
cyclical
What are the 2 main indicators that can be used to calculate a woman’s fertile period?
body temperature
consistency of cervical mucus
Why are the 2 indicators useful?
as they can be used to predict when a woman will ovulate and therefore when she is most likely to fall pregnant.
What is the method of fertility by using the indicators to predict when a woman will ovulate and therefore when she is most likely to fall pregnant called?
rhythm method
What are the processes of menstruation and ovulation are separated by?
intervals of about 2 weeks
Roughly 1 day after the surge in LH in the bloodstream that triggers ovulation, what happens to a woman’s body temperature?
rises by about 0.2-0.5’c
What happens after the body temperature rises?
it remains at this level for the duration of the luteal phase of the menstrual cycle
How long does the period of fertility last for?
about 1-2 days (after ovulation)
After a third daily recording of this increased body temperature what happens to the period of infertility?
the period of fertility is resumed as the unfertilised egg will have disintegrated
What happens to the cervical mucus during the fertile period?
the cervical mucus is secreted into the vagina
Describe the consistency of cervical mucus during the fertile period?
thinner, slippery and stretchy to allow sperm easy access to the female reproductive system
Why does the consistency of cervical mucus change during the fertile period?
due to the increasing oestrogen levels in the follicular phase
What happens to the consistency of cervical mucus after ovulation?
the mucus gradually increases in viscosity under the action of progesterone, showing that the system has returned to the infertile phase
What has the advancement of modern medicine allowed?
the development of a number of methods which can be used to overcome infertility
Give 4 examples of treatments used to help overcome infertility
stimulating ovulation
artificial insemination
IVF
ICSI
Why might a woman fail to ovulate?
failure of pituitary gland to secrete enough FSH or LH
If a woman fails to ovulate due to the failure of pituitary gland to secrete enough FSH or LH. How can ovulation be successfully stimulated?
by drugs that prevent the negative feedback effect of oestrogen on FSH secretion.
drugs that mimic the normal action of FSH and LH
What can ovulation stimulating drugs cause?
‘super-ovulation’ that can result in multiple births or be used to collect ova for IVF programmes
What is artificial insemination?
the insertion of semen into the female reproductive tract by some other means than sexual intercourse
Why might artificial insemination be used?
if a man has a low sperm count - several samples of his semen can be collected over a period of time and each preserved by freezing . They are defrosted and released into the female’s cerivical region at a time when she is most likely to be fertile.
if Donor semen is required - if the male is sterile, healthy semen samples may be obtained from a donor
What is the problem of infertility caused by which results in the use of IVF?
A blockage of the oviducts
What does IVF enable?
fertilisation to occur outside the bodies of the would-be parents in a culture dish
What can IVF be used in conjunction with and what does this help do?
Pre-implantation Genetic Diagnosis (PGD) to identify single gene disorders an chromosomal abnormalities
What is stage 1 of IVF?
The woman is given hormonal treatment to stimulate multiple ovulation (several eggs released)
What is stage 2 of IVF?
A surgical procedure is employed to remove several of these eggs from around her ovary using a piece of equipment similar to a syringe
What is stage 3 of IVF?
The eggs are mixed with sperm in a culture dish of nutrient medium to allow fertilisation to occur. Alternatively a sperm may be injected directly into an egg at this stage (ICSI)
What is within the nutrient medium?
glucose
amino acids
What is stage 4 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 8 or more cells
What is stage 5 of IVF?
2/3 of the embryos are chosen and then inserted into the vagina into the mother’s uterus (now ready for implantation)
What is stage 6 of IVF?
The raining embryos are frozen and stored in case a second attempt at implantation is required
Why might pre-implantation genetic diagnosis be useful for couples?
couples at risk of having a child with a serious genetic condition
What PGD be used in conjunction with?
IVF to identify single gene disorders and chromosomal abnormalities
In terms of PGD, what happens during IVF before the embryo is inserted into the female’s uterus?
a sample of cells is collected from the embryo to test for known chromosomal or gene defects
Why do some people support the use of PGD?
it can offer reassurance to couples who would otherwise be at high risk of producing children with serious genetic disorders.
Why do some people think PGD is morally wrong?
it is morally to interfere with the process of conception by making it selective
What do about 6% of female patients undergoing IVF found to suffer?
hyper stimulation of the ovaries
What can the drugs used during IVF cause?
too many eggs to be produced resulting in the ovaries becoming swollen and sore
What are medical experts concerned that IVF may be exposing many women to?
an increased risk of ovarian cancer in later life
What do most children conceived through IVF tend to have?
lower body mass at birth compared to that of full-term babies
What are children who are born with a low body mass more likely to suffer from?
long-term health problems such as obesity, diabetes, heart conditions an hypertension in later life
What is intra-cytoplasmic sperm injections (ICSI)?
when only one sperm is injected directly into an egg cell
What happens to the sperm before it is injected into the egg during ICSI?
It is immobilised by removing its tail
Describe ICSI?
The head of sperm is drawn into a needle and injected directly into the egg to achieve fertilisation.
When is ICSI commonly used?
if mature sperm are defective or very low in number
What is contraception?
the intentional prevention of conception or pregnancy by natural or artificial means
What does the rhythm method depend on ?
the women developing a sound knowledge of her own menstrual cycle. She can, with practice, be confident in her ability to identify her fertile and decide to abstain from sexual intercourse at this time. This information can also be useful if a couple is having difficulty in conceiving as they would then intercourse at this time to increase their chances
Name a natural method of contraception?
rhythm method
What are the 2 categories of artificial contraception?
Physical (barrier)
chemical
What does a barrier method do?
physically blocks the ability of sperm to reach an ovum
Give 3 examples of barrier methods of contraception?
condoms
diaphragm
sterilisation
What is sterilisation?
a medical technique which permanently prevents a person from being able to reproduce
What is sterilisation in men called?
a vasectomy
What is sterilisation in women called?
tubal ligation
How effective is sterilisation?
it is a highly effective means of contraception but it is normally irreversible
What does a vasectomy involve?
the cutting and tying of the two sperm ducts preventing sperm being released from the testes
What does tubal ligation involve?
the cutting and tying of the two oviducts to prevent eggs meeting sperm and reaching the uterus
What are chemical contraceptives based on?
combinations of synthetic hormones that mimic negative feedback preventing the release of FSH/LH
Who are chemical contraceptives only available for?
Females
How are chemical contraceptives usually taken?
orally as a daily pill
What do all formulations of hormones contain?
synthetic forms of oestrogen and/or progesterone
What are the 2 main types of contraceptive pill?
progesterone only pill
morning after pill
What progesterone only pills also called?
mini pill
What do mini-pills contain?
only very high concentrations of synthetic progesterone
How do mini-pills work?
by causing the thickening of cervical mucus, which reduces the viability of sperm and their access to the egg
What is the morning after pill also known as?
emergency hormonal contraception pills
What does the morning after pill often contain?
higher doses of the hormones (progesterone and oestrogen) found in standard oral contraceptive pills.
When are the morning after pills taken?
after unprotected sexual intercourse to prevent implantation from occurring if fertilisation has taken place unintentionally
Ideally when should the morning after pills be taken?
as soon after unprotected sex as possible but may be effective up to 72 hours
