1. REPRODUCTION
Topic 6.6
IB Biology
Miss Werba

2. NERVOUS & ENDOCRINE SYSTEMS
TOPIC 6 - PHYSIOLOGY
6.1
DIGESTIVE SYSTEM
6.2
CIRCULATORY SYSTEM
6.3
IMMUNE SYSTEM
6.4
RESPIRATORY SYSTEM
6.5
NERVOUS & ENDOCRINE SYSTEMS
6.6 REPRODUCTIVE SYSTEM
J WERBA – IB BIOLOGY 2

3. THINGS TO COVER
Structure of the adult male and female Reproductive Systems
Role of hormones in the menstrual cycle
Graph of hormone levels in the menstrual cycle
Role of testosterone in males
In vitro fertilisation (IVF):
Process
Ethical issues
Risks
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4. THE MALE REPRODUCTIVE SYSTEM Command term = DRAW and LABEL
6.6.1
THE MALE REPRODUCTIVE SYSTEM Command term = DRAW and LABEL
bladder
vas deferens
seminal vesicles
prostate gland
Cowper’s gland
urethra
scrotum
penis
epididymis
testis (pl. testes)
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5. THE MALE REPRODUCTIVE SYSTEM
6.6.1
THE MALE REPRODUCTIVE SYSTEM
Process of sperm production in tests = spermatogenesis
Epididymis can store mature sperm for up to 4 weeks
Vas deferens can store sperm for several months
Alkalinity of semen neutralises acidity of vagina to help improve sperm motility
Sperm move by using their tails like a propeller
Semen contains fructose to nourish sperm and improve motility
Dilation of blood vessels allows penis to become erect
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6. THE FEMALE REPRODUCTIVE SYSTEM Command term = DRAW and LABEL
6.6.1
THE FEMALE REPRODUCTIVE SYSTEM Command term = DRAW and LABEL
fallopian tube
funnel
ovary
ovarian ligament
uterus
endometrium
uterine wall
cervix
vagina
vulva
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7. THE FEMALE REPRODUCTIVE SYSTEM
6.6.1
THE FEMALE REPRODUCTIVE SYSTEM
Process of ovum production = oogenesis
Fallopian tubes are also known as the oviducts
The endometrium changes throughout the menstrual cycle in preparation for the possible implantation of a fertilised ovum
The vagina contains many organic acids, giving the vagina a very low pH to prevent microbial growth
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8. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
There are 4 hormones involved in controlling the monthly cycle:
FSH – Follicle Stimulating Hormone
LH – Luteinising Hormone
Progesterone
Oestrogen
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9. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
There are 4 hormones involved in controlling the monthly cycle:
FSH – Follicle Stimulating Hormone
LH – Luteinising Hormone
Progesterone
Oestrogen
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10. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
Pituitary gland (in the brain) releases FSH:
stimulates the ripening of the follicle
The growing follicle releases oestrogen:
increases endometrium thickness
inhibits FSH production
stimulates LH production
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11. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
Pituitary gland releases LH:
stimulates ovulation
stimulates corpus luteum formation
The corpus luteum produces progesterone:
maintains endometrium
inhibits FSH production
inhibits LH production
J WERBA – IB BIOLOGY 11

12. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
If fertilisation does not occur:
the corpus luteum degenerates
FSH inhibition by progesterone is lost
the pituitary will start producing FSH again to stimulate another follicle
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13. Pituitary Gland (Anterior Lobe)
6.6.2
HYPOTHALAMUS
FSH LH
Pituitary Gland (Anterior Lobe)
Inhibits FSH
Stimulates LH
Inhibits FSH & LH
Growing follicle
Ovulation
Corpus luteum
Ovaries
OESTROGEN
PROGESTERONE
Builds up endometrium
Maintains endometrium
time/days
Menstruation Menstruation
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14. HORMONES & MENSTRUATION
6.6.2
HORMONES & MENSTRUATION
FSH
OESTROGEN LH
PROGESTERONE
Produced by:
Pituitary
Ovary (follicle)
Ovary (corpus luteum)
Functions:
Stimulates follicle growth
Stimulates oestrogen secretion
Stimulates progesterone secretion
FSH surge stimulates ovulation
Stimulates thickening of endometrium
Promotes secondary sexual characteristics (eg. Breast development, widening of hips)
Stimulates LH secretion
Inhibits FSH secretion
LH surge stimulates ovulation
Stimulates corpus luteum formation
Inhibits ovulation
Maintains endometrium
Inhibits FSH secretion
Inhibits LH secretion
J WERBA – IB BIOLOGY 14

15. Follicular phase Ovulatory phase Luteal phase
6.6.3
Menstruation LH
FSH
progesterone
oestrogen
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16. 6.6.4
TESTOSTERONE IN MALES
Testosterone is a hormone produced by the testes.
It functions to:
Promote the male secondary sexual characteristics (eg. facial and chest hair, extra muscles, deeper voice)
Promotes growth of the male reproductive organs
Spermatogenesis
Enhanced sexual desire (libido)
Enhances immune function
Protects against osteoporosis
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17. IN VITRO FERTILISATION (IVF)
6.6.5
IN VITRO FERTILISATION (IVF)
IVF = in vitro fertilisation
‘in vitro’ literally means ‘in glass’
In this procedure, the egg and the sperm meet outside the female’s body.
First “test tube baby” was Louise Brown, born in 1978.
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18. IN VITRO FERTILISATION (IVF)
6.6.5
IN VITRO FERTILISATION (IVF)
IVF is used for many reasons, including:
Female has blocked oviducts, which can occur due to an earlier infection
Female is unable to produce viable eggs
Female is unable to sustain a pregnancy
Depending on the reasons, it may be possible to use the egg cells of the woman who wants to get pregnant.
If not, donor eggs are used.
J WERBA – IB BIOLOGY 18

19. IN VITRO FERTILISATION (IVF): Process
6.6.5
IN VITRO FERTILISATION (IVF): Process
Drugs used to down-regulate the menstrual cycle:
FSH injected  stimulates multiple follicles to develop
HCG injected  causes follicles to mature
Eggs are harvested/extracted (from the follicles/ovaries)
Semen sample collected and processed to concentrate it.
Healthy sperm is selected.
Semen is brought into contact with the egg to allow fertilization:
sperm is directly injected into egg when low numbers or motility are a factor
semen is mixed with eggs in a dish/outside the body
J WERBA – IB BIOLOGY 19

20. IN VITRO FERTILISATION (IVF): Process
6.6.5
IN VITRO FERTILISATION (IVF): Process
Incubated at 37°C to allow embryos to develop
Dish examined to choose healthiest embryo;
Embryos are placed in uterus/oviduct, using a catheter or frozen so that they can be used later
Pregnancy test/scan used to assess success.
J WERBA – IB BIOLOGY 20

21. IN VITRO FERTILISATION (IVF): Ethics
6.6.6
IN VITRO FERTILISATION (IVF): Ethics
The number of embryos placed in the uterus depends on several factors (including government legislation)
If all embryos were to implant successfully, a multiple pregnancy may result.
This could lead to a premature delivery and a reduced chance of survival for the babies.
J WERBA – IB BIOLOGY 21

22. IN VITRO FERTILISATION (IVF): Ethics
6.6.6
IN VITRO FERTILISATION (IVF): Ethics
Research the ethical issues associated with IVF including the risks to both mother and child(ren).
Make a pros and cons list – with at least 3 ideas on each side of the argument.
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23. Sample questions Q1
The hormones progesterone and LH were measured in a woman’s blood over 40 days. When did her menstrual bleed start?
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24. Sample questions Q2
Outline the roles of FSH in the menstrual cycle. [2]
FSH is secreted by the pituitary gland. During pregnancy, FSH secretion is inhibited. Suggest how FSH secretion could be inhibited during pregnancy. [1] Q3
Discuss the ethical issues surrounding IVF. [6]
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25. Sample questions A1 C A2
FSH stimulates follicle development; FSH stimulates estrogen secretion (by the follicle/ovary);
high levels of progesterone or estrogen inhibit FSH production (during pregnancy)
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26. Sample questions A3 pros/positive considerations: [3 max]
chance for infertile couples to have children;
parents have consciously chosen to have a child;
genetic screening of embryos could decrease suffering from genetic diseases;
spare embryos can safely be stored for future pregnancies/used for stem cell research;
cons/negative considerations: [3 max]
IVF is expensive and might not be equally accessible;
success rate is low therefore it is stressful for the couple;
it is not natural/cultural/religious objections;
could lead to eugenics/gender choice;
could lead to (unwanted) multiple pregnancies with associated risks;
production and storage of unused embryos / associated legal issues / extra embryos may be used for (stem cell) research;
inherited forms of infertility might be passed on to children;
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