2.3 controlling fertility Flashcards
Difference between male and female fertility
Males have continuous fertility from the onset of puberty until death.
Females have cyclical fertility and are only able to conceive for a few days within each menstrual cycle.
When does fertility begin in females
Females are fertile from onset of puberty until menopause so their fertile period is much shorter than males.
How long can ova and sperm survive for?
(Calculate the fertile period within a menstrual cycle of a female 1)
Ova can survive for approximately 24 hours after ovulation. Sperm can survive for approximately 3 days in the female reproductive tract.
When does the fertile period begin?
(Calculate the fertile period within a menstrual cycle of a female 2)
Therefore, the fertile period starts approximately 3 days before ovulation and ends the day after ovulation
When does the fertile period start?
(Calculate the fertile period within a menstrual cycle of a female 3)
In an average 28-day menstrual cycle, assuming that ovulation occurs on day 14, the fertile period would start on day 11 and end on day 15 of the cycle.
For successful fertilisation and implantation the following events must be possible and co-ordinated
Production of viable gametes by both male and female
· Ovum able to travel through fallopian tube
· Sperm able to swim through the female reproductive tract
· Endometrium ready to receive blastocyst for implantation
Infertility is the result when any of these events does not happen.
4 causes of infertility
- failure to ovulate (no ovum released)
-low sperm count
-blockage of fallopian tubes
-failure to implant
what causes a failure to ovulate and a low sperm count?
Likely to be the result of hormone imbalance. Risk factors include : high alcohol intake, smoking, obesity and high stress levels.
Whats the treatment for the failure to ovulate
Treated using fertility drugs that mimic the action of FSH and LH.
treatment of low sperm count
Can be treated using testosterone to boost sperm production. Alternatively, artificial insemination, IVF or ICSI processes could be used
What causes the blockage of fallopian tubes
Can be the result of infection or abnormal tissue growth.
Treatment for blocked fallopian tubes
Surgical treatment to remove blockages or IVF treatment.
What causes the failure to implant
Likely to be the result of hormone imbalance preventing co-ordination between the events in the ovary and the thickening and vascularisation of the endometrium.
Whats the treatment for not being able to implant
Treated using fertility drugs to co-ordinate the ovarian and uterine processes.
does artificial insemination include sexual intercourse
nah
Where is the semen injected (artificial insemination)
female reproductive tract
What is artificial insemination used to treat
Low sperm count
Explain artificial insemination
Collection of several semen samples can be taken over a period of time that are then used to produce a higher quality sample. The semen sample is then inserted into the female reproductive tract using a catheter. If the male is infertile and viable sperm are not produced, semen from a donor can be used for the insemination process.
is ivf surgical or non surgical?
This involves the surgical removal (harvest) of ova from ovaries after hormone stimulation
explain the IVF process
The ova are then mixed with sperm in a culture dish to allow fertilisation to occur. (This is why the technique is called in vitro which means ‘in glass’). The fertilised eggs (zygotes) are then incubated until they have formed at least eight cells (blastocyst stage) and then inserted into the uterus for implantation.
when is ICSI used
This technique is used when mature sperm are defective or very low in number
Explain ICSI
Sperm can be collected after ejaculation or directly from the epididymis or testes. A single sperm is selected and the head of the sperm is drawn into a syringe needle and injected directly into the egg to achieve fertilisation. If fertilisation is successful then the blastocyst is inserted into the uterus for implantation.
what is PGD : Pre-implantation genetic diagnosis
Analysis of the chromosome complement of a developing zygote can be used to identify single gene disorders and chromosomal abnormalities.
what is PGD used for
This can be used as part of a screening process during IVF to identify and any zygotes that are unlikely to result in a viable pregnancy.
State the definition of contraception.
Contraception is the prevention of fertilisation or implantation.
What is a physical method of contraception
These methods place some sort of barrier between the sperm and ovum preventing fertilisation from occurring or preventing implantation.
examples of physical barriers
avoiding intercourse during the fertile period (no intercourse = no pregnancy)
· barrier methods such as condoms, cervical cap and diaphragm – prevent sperm entering the uterus
· intra uterine device (aka IUD or coil) - a small plastic and copper T-shaped device that is inserted into the uterus which disrupts the travel of any sperm and prevents a blastocyst from implanting.
sterilisation procedures in males
In males = Vasectomy – tubes carrying sperm from the testes to the penis are cut, blocked or sealed with heat to prevent sperm entering the semen.
Sterilisation procedures in females
Tubal ligation/occlusion – Fallopian tubes are clamped, blocked or severed and sealed to permanently prevent pregnancy.
spermicides
chemicals that kill sperm. These are often used at the same time as barrier methods to increase the effectiveness.
Chemical contraceptives
Chemical contraceptives are based on combinations of synthetic oestrogen and progesterone hormones. For example :
The combined pill works by inhibiting the release of FSH/LH from the pituitary gland (mimicking feedback control) and so prevent maturation of follicles and ovulation.
mini pill
Progesterone-only (‘mini’) pills work by causing an increase in the volume and viscosity (thickening) of cervical mucus making it impenetrable to sperm so they cannot enter the uterus.
morning after pill
The morning-after pill works by inhibiting ovulation and/or preventing successful implantation.
