Topic 6.6 Reproduction

Question 1

6.6.1 Draw and label diagrams of the adult male reproductive system.

Answer 1

• ​scrotum
• testis
• epididymis
• Vas Deferens (sperm duct)
• bladder
• seminal vesicle
• prostate gland
• erectile tissue
• urethra
• foreskin
• penis

Question 2

6.6.1 Draw and label diagrams of the adult female reproductive system.

Answer 2

• ovary
• fimbriae (finger-like projections near ovary, connected to oviduct)
• oviduct (fallopian tubes)
• uterus
• cervix
• vagina
• vaginal opening
• vulva
• urethra
• bladder

Question 3

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

Answer 3

FSH

• secreted from pituitary gland
• stimulates follicle development
• follicle stimulates estrogen secretion

Estrogen

• makes follicle cells produce more FSH receptors & respond more strongly to FSH (+ feedback) → makes estrogen levels rise
• stimulates repair of uterus lining
• at peak, stimulate LH secretion by pituitary gland

LH

• LH levels at peak causes ovulation
• causes follicles to secrete less estrogen (- feedback) and more progesterone
• after ovulation, promotes follicle’s development into the corpus luteum

Progesterone

• corpus luteum secretes progesterone, which thickens endometrium (uterus lining) in preparation for embyro
• together, high progesterone and estrogen levels inhibit FSH and LH secretion (- feedback)

Question 4

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

Answer 4

Follicular Phase

• FSH stimulates growth of several follicles
• Dominant follicle secretes estrogen
• Estrogen makes follicle cells produce more FSH receptors
  
  • causes estrogen levels to rise
• Estrogen stimulates the repair of the uterus lining
• When estrogen levels are high, + feedback on hypothalamus
  
  • GnRH ↑
  • LH & FSH ↑

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

Note: if fertilisation of egg occurs, the zygote releases a hormone (HCG) which maintains the corpus luteum ∴ keeps making estrogen and progesterone ∴ lining of uterus stays

Question 5

6.6.4 List three roles of testosterone in males.

Answer 5

• maturation of sperm
• development of primary sexual characteristics in male fetus
• maintenance of sex drive

Question 6

6.6.5 Outline the process of in vitro fertilization (IVF).

Answer 6

SHE’S FIT

S top normal menstruation cycle with drugs (3 weeks)

H ormone treatments to develop follicles (10-12 days of FSH injections for follicle development; HCG injection 36 hours prior to egg collection to loosen eggs in follicles and to make them mature)

E xtract multiple eggs from ovaries

S perm collected, processed to concentrate healthiest ones, prepared (capacitation) and injected into egg via intra-cytoplasmic sperm injection (ICSI)

F ertilization occurs under controlled conditions (in vitro)

I mplantation of multiple embryos (2-3) into uterus

T est for pregnancy done a few weeks later to see if embryos have implanted successfully

(scan done a couple weeks later to see if pregnancy is continuing normally)

Question 7

6.6.6 Discuss the ethical issues associated with IVF.

Answer 7

Against IVF

• infertility of parents may be inherited by offspring
• denies unused embryos the chance of life
• placing fate of new individuals in hands of embryologists, humans
• IVF is expensive, not accessible to everyone
• cultural and religious objections to embryo creation in unnatural way
• success rate is low, may be stressful for couples
• may lead to multiple pregnancies (couple cannot afford) and may involve extra birth risks
• may lead to eugenics (controlled breeding to promote desired characteristics)

For IVF

• many types of infertility due to environmental factors ∴ offspring won’t inherit infertility
• embryos haven’t developed nervous systems, can’t feel pain
• genetic diseases can be decreased by screening embryos
• spare embryos can be stored for future pregnancies/stem cell research
• a chance for infertile couples to have children