6.6: Reproduction

Question 1

Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone, LH (luteinizing hormone), estrogen and progesterone:

Answer 1

FSH (Secreted from anterior pituitary):

• Stimulates follicular growth.
• Stimulates estrogen secretion (from developing fossicle).

Estrogen (Secreted from Ovaries):

• Development of endometrium.
• Stimulates LH secretion (follicular phase).
• Inhibits LH and FSH (luteal phase).

LH (Secreted from anterior pituitary):

• Surge causes ovulation.
• Development of corpus luteum.
• Stimulates progesterone secretion.

Progesterone (Secreted from Ovaries):

• Thickening of endometrium.
• Inhibits LH and FSH (luteal phase).

Question 2

Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and the thickening of the endometrium:

Answer 2

Follicular Phase:

• FSH stimulates growth of several follicles
• Dominant follicle secretes estrogen
• Estrogen inhibits growth of other follicles (and FSH)
• Estrogen stimulates development of endometrium

Ovulation:

• A surge in LH causes ovulation (egg release)
• Rupturing of follicle creates a corpus luteum

Luteal Phase:

• Corpus luteum secretes progesterone (and estrogen)
• Progesterone stimulates development of endometrium
• Estrogen and progesterone inhibit FSH and LH
• Corpus luteum degrades over time
• When corpus luteum degrades, progesterone levels drop
• Without progesterone, endometrium cannot be maintained
• Endometrium is sloughed away (menstruation)
• No longer inhibited, FSH can start menstrual cycle again
• If fertilisation of egg occurs, the zygote releases a hormone (hCG) which maintains the corpus luteum

Question 3

List three roles of testosterone in males:

Answer 3

1. Stimulates the development of prenatal genitalia.
2. Stimulates the development of the male secondary sexual characteristics such as growth of the skeletal muscle and pubic hair.
3. During adulthood it maintains the sex drive.

Question 4

Outline the process of in vitro fertilization (IVF):

Answer 4

1. For a period of three weeks, the women has to have a drug injected to stop her normal menstrual cycle.
2. After these three weeks, high doses of FSH are injected once a day for 10-12 days so that many follicles develop in the ovaries of the women.
3. HCG (another hormone) is injected 36 hours before the collection of the eggs. HCG loosens the eggs in the follicles and makes them mature.
4. The man needs to ejaculate into a jar so that sperm can be collected from the semen. The sperm are processed to concentrate the healthiest ones.
5. A device that is inserted through the wall of the vagina is used to extract the eggs from the follicles.
6. Each egg is then mixed with sperm in a shallow dish. The dishes are then put into an incubator overnight.
7. The next day the dishes are looked at to see if fertilisation has happened.
8. If fertilisation has been successful, two or three of the embryos are chosen to be placed in the uterus by the use of a long plastic tube.
9. A pregnancy test is done a few weeks later to find out if any of the embryos have implanted.
10. A scan is done a few weeks later to find out if the pregnancy is progressing normally.

Question 5

Discuss the ethical issues associated with IVF:

Answer 5

Arguments for:

• Many types of infertility are due to environmental factors rather than genetic which means that the offspring would not inherit the infertility.
• The embryos that are killed during the IVF process cannot feel pain or suffering as they do not have a developed nervous system.
• Suffering caused by genetic diseases can be decreases by screening the embryos before placing them into the uterus.
• Since the IVF process is not an easy one emotionally and physically, is costly, takes time and there are no guarantees, parents who are willing to go through it must have a strong desire to have children and therefore are likely to be loving parents.
• Infertility can cause emotional suffering to couples who want to have children. IVF can take away this suffering for some of those couples.

Arguments against IVF:

• The infertility of the parents may be inherited by their offspring passing on the suffering to the next generation.
• More embryos are produced than needed and the ones that remain are usually killed which denies them the chance of a life.
• Embryologists select which embryos will be placed into the uterus. Therefore they decide the fate of new individuals as they choose which ones will survive and which ones will die.
• IVF is not a natural process which takes place in a laboratory compared to natural conception which occurs as a result of an act of love.
• Infertility should be accepted as God’s will and to go against it by using IVF procedures would be wrong.