Key area 3 : the biology of controlling fertility

Overview (men)

• in men, there is a relatively constant level of FSH and ICSH in the bloodstream

• Therefore, a steady Quantity of testosterone is secreted and a steady quantity of sperm produced

• As a result, men show constant fertility

Overview (women)

• Women show cyclical fertility which means they are only fertile for a few days during each menstrual cycle

• Cycle fertility is marked contrast in with the continuous fertility in males

Indication of the Fertile period

• temperature and mucus can be used by a woman to calculate her fertile period

• This is a used a couples Who are wishing to conceive

Temperature

• approximately one day after the LH surge which triggers ovulation, a woman’s body temperature rises by about 0.5°C

• It remains at this elevated level for remainder of the luteal phase

• The fertile period loss for about 1 to 2 days

• The infertile period is resumed after the third daily recording of high temperature

Mucus

• The cervical mucus secreted into the vagina during the fertile period becomes thin and watery

• This allows easy access of sperm into the female reproductive system

• After ovulation, progesterone causes the mucus to gradually increase in viscosity

Treatment for infertility - overview

Sometimes there is a failure of the pituitary gun to secrete adequate FSH or LH and a woman fails to ovulate

Stimulating ovulation

• ovulation can be stimulated by drugs that prevent negative feedback effect of oestrogen on FSH secretion

• Ovulation can be stimulated by drugs that mimic the normal action of FSH and LH

• These drugs can be so effective that they bring about super ovulation in which several over are released at once and can lead to multiple births.

Artificial insemination

• this involves the insertion sperm into the female tract by some means other than sexual interface

• It is particularly useful where a male has low sperm count

• Several samples of semen are collected and each was preserved (freezed) until required

• They are then defrosted and released together into the partner cervical region during her photo period

• If a partner is sterile, artificial insemination can be used to insert the semen of a donor who has a normal sperm count into the female reproductive tract

ICSI

• this technique is employed when a man’s sperm count is low or, many of the sperm are defective

• The procedure involves drawing a healthy sperm into the needle and injecting it directly into an egg to achieve fertilisation

Reasons for IVF

IVF overcomes the problem of infertility caused by a blockage of the oviducts.

Stage 1 of IVF

• Woman is given hormone treatment to stimulate multiple ovulation

Stage two of IVF

• The eggs are surgically removed from the ovary using equipment like a syringe

Stage three of IVF

• Eggs are mixed with sperm in a culture dish, containing nutrients, to allow fertilisation to take place. Alternatively, sperm may be injected directly into the egg using ICSI.

Stage four of IVF

• Fertilise eggs are incubated for 2 to 3 days to perform embryos of at least eight cells or more

• Pre-implantation genetic diagnosis (PGD) can be employed at this stage to identify genetic disorders and chromosome or abnormalities

Stage five of IVF

• 2/3 Ambrose are inserted into the uterus for implantation

• Remaining reels are frozen in case a second attempt is needed

Overview of contraception

• contraception is the intentional prevention of conception Of pregnancy by natural or artificial means. Avoidance of fertile period would be an example of a natural method of contraception.

What are physical maths of contraception?

The barrier method physically blocks the ability of the sperm to reach the ovum

Condom

Fits over penis

Diaphragm

Dome shaped rubber cap inserted into the vagina blocking the cervix

Cervical cap

Rubber structure which fits tightly around the cervix and can be left in place for a few days

Intra Uterine Device

• an IUD is a plastic T-shaped structure with a copper wound around its outside

• It is fitted into the uterus for several years

• It has threads attached for easy removal by doctor

• It prevents the implantation of an embryo

• The presence of an IUD stimulates the presence of white blood cells which are hostile to sperm and embryo

• It impairs the mobility of sperm

• It irritates the lining of the uterus, making it unreceptive To the embryo

• IUD can cause complications, information of these an ectopic pregnancy

Sterilisation procedures

• Vasectomy

• Tubal ligation

Vasectomy

• this involves cutting and tying the two sperm duct

• This prevents sperm being released. The sperm produced undergo phagocytosis.

Tubal ligation

• this involves cutting and tying the two oviducts

• This prevents egg meeting sperm

Chemical methods of contraception

• pills containing a combination of hormones

• Morning after pill

• Mini pills

Pills containing a combination of hormones

• oral contraceptive pills usually contain synthetic oestrogen combined with synthetic progesterone

• The pill is taken every Day for three weeks from the final day for the previous menstrual perio

• This increases the concentration of oestrogen and progesterone in the bloodstream and exerts negative feedback control

How do pills containing a combination of hormones work

• Secretion of FSH and LH by the pituitary gland is inhibited

• Follicle maturation remains inhibited and ovulation does not occur

• Placebo pills are taken during week 4 to allow oestrogen and progesterone levels to decrease, as a result ministration takes place

Morning After pill

• contain higher doses of hormones than the standard oral contraceptive pill

• They are taken after unprotected sex to prevent ovulation or implantation of an embryo in the uterus if fertilisation has occurred

Mini pill

• these are known as progesterone only pills because they do not contain synthetic oestrogen

• Mini pills thicken the cervical mucus, reducing the viability of sperm

• This form of contraception can also be given as an implant under the skin

• You can be used to give production for up to 3 years

Advantages of mini pill are

• can be used during breastfeeding

• Can reduce cramps and heavy bleeding

• Can be taken by women who cannot take oestrogen

• Can be taken by women who have high blood pressure

Disadvantages of mini pills

• must be taken at the same time every day

• can cause breast tenderness

• Can cause mood swings

• Can lead to weight gain

• Can lead to. Irregular menstruation