Unit 2 3 The biology of controlling fertility

Question 1

Identification of the fertile period.

Answer 1

A woman’s body temperature rises by around 0·5°C after ovulation and her cervical mucus becomes thin and watery.

Question 2

Stimulating Ovulation

Answer 2

Ovulation is stimulated by drugs that prevent the negative feedback effect of oestrogen on FSH secretion.
Other ovulatory drugs mimic the action of FSH and LH. These drugs can cause super ovulation that can result in multiple births or be used to collect ova for in vitro fertilisation (IVF) programmes.

Question 3

Artificial inseminatioN

Answer 3

Several samples of semen are collected over a period of time. Artificial insemination is particularly useful where the male has a low sperm count. If a partner is sterile a donor may be used to provide semen.

Question 4

Intra-cytoplasmic sperm injection (ICSI)

Answer 4

If mature sperm are defective or very low in number, ICSI can be used. The head of the sperm is drawn into a needle and injected directly into the egg to achieve fertilisatioN

Question 5

In vitro fertilisation (IVF)

Answer 5

Surgical removal of eggs from ovaries after hormone stimulation. Incubation of zygotes and uterine implantation. The use of IVF in conjunction with pre-implantation genetic diagnosis (PGD) to identify single gene disorders and chromosomal abnormalities.
Eggs are mixed with sperm in a culture dish. The fertilised eggs are incubated until they have formed at least eight cells and are then transferred to the uterus for implantation

Question 6

Emergency hormonal contraceptive pills prevent or delay ovulation.

Answer 6

These pills are often referred to as ‘morning- after’ pills, but they can be taken up to 72 hours or 120 hours after unprotected sex, depending on which type of pill is usEd

Question 7

The progesterone-only (mini) pill

Answer 7

causes thickening of the cervical mucus

Question 8

Intra-uterine device (IUD)

Answer 8

Prevents implantation of an embryo into the endometrium.

Protects against pregnancy for between 5 and 10 years.

It’s sometimes called a “coil” or “copper coil”.

Question 9

Male Sterilisation

Answer 9

Males:
Vasectomy – sperm ducts are cut and tied to prevent sperm being released.
Glandular secretions are still produced and released during ejaculation.

(Any sperm produced after sterilisation are destroyed by phagocytosis and reabsorbed)

Question 10

Female Sterilisation

Answer 10

Tubal ligation – oviducts are cut and tied to prevent the egg meeting the sperm and reaching the uterus.

Question 11

Barrier Methods

Answer 11

Stop sperm from reaching Ovum and examples include condom, Diaphragm and Cervical Cap

Question 12

pre-implantation genetic diagnosis (PGD)

Answer 12

The use of IVF in conjunction with pre-implantation genetic diagnosis (PGD) to identify single gene disorders and chromosomal abnormalities.