reproduction (part 2)

Question 1

Puberty triggers the release of which 2 hormones?

Answer 1

• Follicle-stimulating hormone (FSH)
• Luteinising hormone (LH)
  (hypothalamus)

Question 2

The reproductive/menstrual cycle repeats every __ days on average, but cycles from __ to __ days are not uncommon.

Answer 2

The reproductive cycle repeats every 28 days on average, but cycles form 20 to 40 days are not uncommon.

Question 3

What are the two cycles in the menstrual/reproductive cycle?

Answer 3

• Ovarian cycle (monthly prep + shedding of an egg cell from an ovary)
• Uterine cycle (buildup of uterus lining)

Question 4

What is menstruation?

Answer 4

Menstruation is uterine bleeding caused by the breakdown of the endometrium, the blood-rich inner lining of the uterus.

Question 5

Menstruation usually lasts __-__ days. After menstruation, the endometrium regrows, reaching its maximum thickness in __-__ days. (if embryo is not implanted in uterine wall)

Answer 5

Menstruation usually lasts 3-5 days. After menstruation, the endometrium regrows, reaching its maximum thickness in 20-25 days. (if embryo is not implanted in uterine wall)

Question 6

What are the stages of the menstrual cycle?

Answer 6

1. FSH (follicle-stimulating hormone) stimulates growth of follicles in ovary
2. Developing follicles secrete oestrogen, which stimulates buildup of endometrium + prevents further secretion of FSH (negative feedback 1)
3. Peak levels of oestrogen occurs about midpoint of cycle. High and sudden peak stimulates secretion of LH.
4. Surge in LH stimulates ovulation and conversion of follicle tissue to corpus lutem.
5. Corpus lutem secretes progesterone and some oestrogen. This continues buildup of endometrium, allowing it to become thickened, and inhibits further secretion of LH and FSH (negative feedback 2).
6. Falling levels of LH and FSH causes corpus lutem to degenerate. As a result, progesterone and oestrogen decreases, the endometrium breaks down, and the menstrual cycle starts from the beginning.

Question 7

What happens when implantation (with fertilisation) occurs?

Answer 7

Fertilised egg/embryo secretes a hormone called human chorionic gonadotropin (hCG). hCG maintains the corpus luteum, which continues to secrete oestrogen and progesterone, keeping the endometrium intact.

Question 8

hCG applications in daily life?

Answer 8

• Most home pregnancy tests work by detecting hCG in urine

- In males, hCG boosts testosterone production, so its use is banned in many sports organisations.

Question 9

Fertilisation is…

Answer 9

Fertilisation is the union of a sperm and egg, forming a zygote (first cell produced).

Question 10

Conception is…

Answer 10

Conception is a process that starts with fertilisation and ends with implantation of an embryo, resulting in pregnancy.

Question 11

Ovulation releases matured egg –> sperm fertilises ovum, forming a zygote –> what’s next?

Answer 11

Cleavage (cell division) of embryo starts –> develops into a blastocyst –> The blastocyst implants in the endometrium.

Question 12

Human chorionic gonadotropin (hCG) will be produced by the ____ to maintain the corpus lutem, which produces ____ to maintain the thickness of the endometrium.

Answer 12

Human chorionic gonadotropin (hCG) will be produced by the blastocyst to maintain the corpus lutem, which produces progesterone to maintain the thickness of the endometrium.

Question 13

Once the placenta is fully formed at around week 8, hCG levels will ___. The placenta will start producing progesterone.

Answer 13

Once the placenta is fully formed at around week 8, hCG levels will drop. The placenta will start producing progesterone.

Question 14

What is the placenta?

Answer 14

It is the organ that provides nourishment and oxygen to the embryo and helps dispose of its metabolic wastes. It has chorionic villi closely associated with the blood vessels of the endometrium.

Question 15

About a month into fertilisation, the amnion will enclose the embryo. How does the amnionic fluid protect the embryo?

Answer 15

• Protection (cushion from external trauma)
• Constant temperature
• Allows for free movement for foetal (muscle) development
• Practice swallowing (feeding after birth)
• Will lubricate vagina when breaks just before childbirth

Question 16

What are the functions of chorionic villi?

Answer 16

Chorionic villi are finger-like structures developed by the embryo.

• Helps the embryo implant itself into the endometrium
• Absorbs nutrients and oxygen from the mother’s blood and passes substances to the embryo via chorionic blood vessels
• Waste products diffuse to the mother’s bloodstream via chorionic villi

Question 17

The placenta does not always prevent substances circulating in the mother’s body from reaching the embryo. Name some of these substances.

Answer 17

• Viruses
• Drugs (including prescription medication)
• Alchohol
• Chemicals in cigarette smoke

Question 18

What is the umbilical cord and its function?

Answer 18

It is a circulatory pathway that connects the embryo to the chorionic villi of the placenta.
It transports oxygen and nutrients to the foetus and waste products from the foetus to the placenta.

Question 19

Umbilical arteries carry _____ blood from the foetus back to the placenta.
Umbilical vein carries _____ blood from the placenta to the foetus.

Answer 19

Umbilical arteries carry deoxygenated blood from the foetus back to the placenta.
Umbilical vein carries oxygenated blood from the placenta to the foetus.

Question 20

Infertility is…

Answer 20

Infertility is a condition in which couples who want children are unable to conceive even after 12 months of unprotected intercourse.

Question 21

How does IVF (in vitro fertilisation) work?

Answer 21

Eggs are surgically removed from the ovaries after hormonal stimulation, mixed with sperm in culture dishes and incubated for several days so that fertilised eggs start developing.
When they have developed into embryos of at least 8 cells each, they are carefully inserted into the woman’s uterus.

Question 22

List down some contraception methods (behavioural, surgical, physical, chemical)

Answer 22

Temporary abstinence, withdrawal method, sterilisation surgery (tubal ligation / vasectomy), barrier methods (diaphragms, condoms, cervical caps), intra-uterine device (IUD), birth control hormones, morning after pill

Question 23

What are some reasons for infertility in men and women?

Answer 23

Males:

• Low sperm count / defective sperm
• Impotence / erectile dysfunction

Females:

• Lack of eggs / failure to ovulate
• Blocked fallopian tubes
• Inability to support growing embryo

Question 24

Why is temporary abstinence ineffective/unsuitable for some women?

Answer 24

• Depends on how regular one’s menstrual cycle is as this method assumes ovulation takes place around the 14th day
• Sometimes women may ovulate at an unexpected time period
• Ovulation can also be detected with other methods, e.g. detecting changes in cervical mucous (stretchable and clear) / changes in body temperature

Question 25

What is the withdrawal method and why is it unreliable?

Answer 25

• Penis is withdrawn moments before ejaculation
• Sperm is not released in the vagina, so reduced chances of pregnancy
• Not a very reliable method as sperm is released during intercourse and not only during ejaculation

Question 26

What is sterilisation surgery for men and women called? Is it temporary or permanent?

Answer 26

• Permanent! (very reliable).
• Oviducts are cut and tied off: tubal ligation
• Sperm duct cut: vasectomy

Question 27

What are some barrier methods?

Answer 27

• Diaphragms: dome-shaped rubber cap that covers the cervix

- Condoms: sheaths usually made of latex that fit over the penis / within the vagina

Question 28

How does an IUD work?

Answer 28

• Presence of foreign body within uterus provokes an immune response against sperms and eggs
• (copper in some IUDs enhances this immune response)
• (hormones in IUDs inhibit ovulation)
• also has an effect against implantation

Question 29

How do birth control pills work?

Answer 29

• They contain 2 hormones that are chemically similar to oestrogen and progesterone
• Prevent ovulation, thicken cervix mucus, make endometrium thinner
• Hormones prevent ovulation by decreasing the release of FSH and LH (negative feedback)
• Restricts the growth of follicles in ovaries (therefore no ovulation)