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Powerpoint Presentation: Human Reproduction
Powerpoint Presentation: Fertilisation
Powerpoint Presentation: Sex Development
Powerpoint Presentation: In Vitro Fertilisation (IVF)
Powerpoint Presentation: The Embryo
Powerpoint Presentation: Labour

 

Animal Physiology Index

The Nervous System and Movement
Muscle contraction
The Nerve Impluse
The Synapse
The Major Factors controlling the Heartbeat
Defence Against Disease
Digestion
The Alimentary Canal or Gut

Topic Chapters Index


Contraception:

Approximate Number of Pregnancies during the first year of use for 100 non-sterile women initiating the method.

Method

Used correctly and consistently

Average amongst 100 women wanting no more children

Abortion

0

0

Sterilisation: Women: Tubal ligation

0.4

0.04

Sterilisation: Men: Vasectomy

0.15

0.15

Oral contraceptive (The Pill)

0.34

4 to 10

Injections: (DEPO-PROVERA)

0.25

5 to 10

Condom + Spermicide

1

5

Minipill

1 to 1.5

5 to 10

I.U.D.

1 to 3

5

Condom only

3

10

Diaphragm + Spermicide

3

17

Spermicidal foam only

3

22

Coitus Interruptus

9

20 to 25

Rhythm Method

13

21

Lactation for 12 months *

25

40

Douche

?

40

No method

90

90

ANIMAL PHYSIOLOGY

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Reproduction

Contraception:

Sterilization of the female

Several techniques are used all usually irreversible.

Hysterectomy: the total removal of the uterus; Laparotomy the ligation (tying) of the fallopian tubes, entry into the abdomen by a small incision. Alternatively, entry by endoscope through the navel or vagina. The woman could in theory have another child by the implantation of an egg fertilised in vitro (test-tube baby). No change in menstrual cycle.

Sterilization of the male

Vasectomy, the cutting of the vas deferens, which is an irreversible operation. The sperm duct must be cleared of spermatozoa, this can take up to 6 months. Spermatozoa could be stored in liquid nitrogen for future artificial insemination. No change in ejaculation or hormone levels.

Sterilisation is usually only prescribed for a parent of established families (i.e. with children already) or where there is a risk to the mother's health in subsequent pregnancies or if the parent is a carrier of a genetic disease.

The Birth Control Pill

This works on the basis that FSH is inhibited by oestrogen during pregnancy thus preventing further ovulation. Synthetic oestrogens and progestins are present in the pill which is taken daily for a three week period. The dose is stopped for one week to allow a menstrual bleed. Thus the ovaries are permanently inhibited from ovulating.

Side effects include: Blood clots, hypertension, cancer risk, diabetes, nervous depression, nausea (usually for the first 2 months), fatigue, vaginal discharge, weight gain, a more regular menstrual cycle and a disappearance of menstrual cramps. These vary considerably with. the woman. All women who take the pill are advised to consult their doctor regularly and to have a blood and cervical smear test at least once a year.

The mini pill

Progesterone only in a low dose. This tries to reduce the risk of side effects. Its contraceptive effectiveness is reduced dramatically if one pill is forgotten or in periods of illness where the bodies metabolism is elevated (e.g. fever). The mini pill is usually taken continuously without interruption.

Injections

DEPO-PROVERA (Depot Medroxyprogesterone acetate). A long lasting birth control method. Injections every 3 to 6 months.

Side effects: Disruption of menstrual bleeding, possible association with cervical cancer and other effects similar to oral contraception.

The morning after pill

These have existed for many decades but recently the introduction of mifepristone (RU486) has made the treatment much safer. Taken under medical supervision within 4 weeks of unprotected sex, it can be used to block a pregnancy and precipitate a miscarriage by inhibiting the progesterone receptors of the uterus. The lining of the uterus loosens and a menstrual bleed starts with the loss of the implanted embryo.

Side effects: Some nausea, headache, weakness, diarrhoea and/or fatigue. Uterine infections are possible. It is not a treatment recommended for heavy smokers or women with high blood pressure.

Intrauterine Device (IUD), Coil or Loop

A plastic or metal device inserted into (and removed from) the uterus by an expert. Mode of operation not certain. It is possible that it irritates the endometrium triggering prostaglandin release causing uterine contractions and preventing implantation. Usually prescribed to women who have already had one child.

Side effects: Injury to the uterus, excessive menstrual bleeding, possible sterility.

Diaphragm or Cap with Spermicidal Jelly or Cream

Various sizes used to fit over the cervix.

Disadvantages: it takes practice to insert properly, it requires a certain amount of premeditation and preparation. The cap needs to be checked once a year.

Side effects: None, though irritation and allergies to the spermicide may cause problems.

Condom or Sheath

Very effective if used properly and nearly 100% effective if used with creams or foams. Placed over the erect penis well before intercourse. After intercourse removal of the condom should be carried out with care.

Side effects: None though lubricants may cause allergies.

Foam Spermicide

A physical and chemical barrier applied in front of the cervix. Not so effective on its own but very effective when combined with a condom or a diaphragm.

Disadvantages: Must be applied just before intercourse.

Side effects: None though it may cause irritation or allergies.

Rhythm Method

Being aware of her menstrual cycle a woman can to a certain degree predict when ovulation takes place. Use of indicators such as the menstrual bleed, the cervical mucus which changes in texture or body temperature which dips slightly just before ovulation and rises after it. The "safe period" being at least 3 days before ovulation (sperm can live in the uterus/vagina for up to 3 days) and. 36 hours after it (the egg lives for 36 hours but is receptive for about 24h).

Disadvantages: Some women have very variable cycles. Some women are reflex ovulators, ovulating after sexual intercourse no matter what stage of the cycle.

Withdrawal or Coitus Interuptus

Removal of the penis from the vagina just before ejaculation of the semen. Not very effective. Can lead to nervous tension and. disruption of the relationship.

Lactation

Prolactin, the milk secretion hormone, produced. by the pituitary after birth inhibits FSH and therefore ovulation. However, it only works effectively if the baby is fed milk when it wants it. Any attempt to train the baby into a socially acceptable daily feeding rhythm appears to upset the contraceptive value of breast feeding. Pre-weaning or bottle feeding the baby will also reduce the level of prolactin sooner.

* Reference: R.V. Short (1984) Breast Feeding. Scientific American April p.23.

Non-methods

A lot of mythical methods have developed. including douching (squirting a liquid into the vagina after intercourse), sperms swim too fast; dislodging the sperm by standing up, holding your breath, jumping up and. down after intercourse; not allowing the penis to completely penetrate the vagina - they do not work.

 

In Vitro Fertilisation (IVF)

The fertilisation of an oocyte by a sperm from a male and a female donor outside the woman, with the subsequent implantation of the early embryo into a receptive female's uterus.

 

The method

  • A woman is induced to ovulate by giving her a treatment with the hormone FSH.

  • HCG is used 36 hours before collection to mature the oocytes and loosen them in their follicles.

  • The oocytes she produces are collected by laproscopy (a catheter or tube is guided into the abdomen) from mature follicles on the surface of the ovary.

  • The collected oocytes are separated from the follicular liquid.

  • Sperms are harvested from a male by ejaculation, the sperms are washed to activate them (capacitation) and selected for good motility.

  • 20 000 sperms are placed in a dish with one oocyte in a culture medium similar to that found in the fallopian tube of a woman. They are left for 2 to 6 hours.

  • The zygotes are placed in a sperm free medium.

  • The embryos are left to develop for 3 days and the best are selected for implantation.

  • Implantation of 2 or 3 embryos in a receptive mother.

  • Implantation can be in the same woman who donated the oocyte. In which case the timing must be right, 7 - 10 days after ovulation.

  • Implantation could be carried out in another woman (surrogate mother) who has had hormone treatment to prepare her uterus for implantation.

 

Ethical Issues

For

  • IVF can permit childless couples to have their own children

  • IVF can be used to select embryos which can survive in couples which carry genetic diseases.

  • The use of surrogate mothers could permit professional women to continue their careers.

Against

  • Not all the embryos created are used, so some will be destroyed yet they can be considered individuals.

  • The method for obtaining the oocytes from the mother are not without some risks.

  • Women are implanted with several embryos which increases the chances of multiple births. This places the mother and her babies at risk.

  • IVF could increase the chances of babies with congenital problems being born.

    Under natural conditions:

    For 100 oocytes exposed to sperms

    oocytes exposed to sperms

    IVF is 0 - 25% successful so it does not seem to be encouraging the birth of children affected with congenital problems.

     
  • It could lead to selective breeding (eugenics).

    Yes it could be abused to promote particular characteristics (positive eugenics)

    It is already being used to eliminated undesirable characteristics (negative eugenics) such as congenital problems.

  • It could encourage the involvement of surrogate mothers.

    Indeed all sorts of possible combinations are possible, sperm donors, oocyte donors, surrogate mothers.

  • Babies could be specially conceived using IVF to provide cells for brothers and sisters with congenital problems.

    This has been done, the stem cells can be extracted from the umbilical cords of a new born baby and transplanted into another person.

    Thus several attempts are made to create the right individual but only embryos with the desired criteria are retained.

 

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