1. Ch15: Sex Organs & Hormonal Control
Higher Human Biology

2. Male Reproductive System
Testes are the site of:
sperm production
manufacture of the male sex hormone testosterone

3. Sperm Production
Sperm are formed by meiosis in the tiny seminiferous tubules of the testes, which unite forming coiled tubes that connect to the sperm duct.
Sperm duct

4. Sperm forming by meiosis

5. Pathway of sperm

6. Pathway of sperm during sexual intercourse
Image source:
Sperm are motile. This requires a fluid medium & a source of energy.

7. Testosterone ….the male sex hormone
Produced by interstitial cells, in the tissue between the seminiferous tubules of the testes
Released directly into the bloodstream
Image source:

8. Seminal Vesicles
Males have 2 seminal vesicles, which secrete a thick liquid rich in:
fructose – a sugar that provides sperm with energy for motility
prostaglandins – hormone-like compounds that stimulate contractions of the female reproductive tract. Help sperm to move more quickly towards the egg.

9. Prostate Gland
Secretes a thin lubricating liquid containing enzymes. The enzymes keep the fluid at the optimum viscosity (thickness) for sperm motility.
Semen is a milky liquid composed of:
sperm,
fluid from seminal vesicles
fluid from prostate gland

10. Female Reproductive System
Oviduct / Egg tube Where the egg is fertilised
Ovary
Produces eggs
Uterus lining
Lining of the womb
Uterus / Womb
Where the baby grows
Cervix
The neck of the uterus which connects to the vagina.
Vagina
The penis is put here when mating.

11. Developing Egg
Eggs are formed by meiosis in the ovaries. Each ovum (egg) is contained by a developing Graafian follicle which secretes oestrogen (a hormone).
After ovulation (release of the egg), the Graafian follicle develops into a corpus luteum which secretes the hormone progesterone.

12. Image source: http://resources.schoolscience.co.uk

13. Hormones
Hormones are chemical messengers, produced in the endocrine (ductless) glands (e.g. pituitary and thyroid glands) then secreted into the bloodstream.
Pituitary gland
When a hormone reaches its target tissue it brings about a specific effect
Thyroid gland

14. Gonadotrophic hormones
The gonads (reproductive organs) are the target organs of two of the hormones produced by the pituitary gland, thus these hormones are called gonadotrophic hormones:
FSH: follicle-stimulating hormone
ICSH: interstitial cell- stimulating hormone (males)
LH: Luteinising hormone (females)
These hormones begin to be released from the anterior pituitary at puberty.

15. Male Gonadotrophic hormones
promotes sperm production in the seminiferous tubules
The functions of the testes are regulated by these hormones:
Anterior
(front)
lobe
FSH
In bloodstream
Testosterone
stimulates interstitial cells to produce testosterone
ICSH
Activates secretion from prostate gland + seminal vesicles

16. Self Regulation of Testosterone
The body has self-regulating mechanisms, called negative feedback control, that allows the body to correct changes.
When the concentration of testosterone gets to a certain level it inhibits the secretion of FSH & ISCH, which in turn causes a decrease in testosterone concentration.

17. Negative Feedback Control
When a factor affecting the body’s internal environment deviates from its norm (or set-point) the body responds to correct the change.
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18. Female Gonadotrophic hormones
FSH stimulates:
Development and maturation
of each Graafian follicle
Secretion of oestrogen
from ovary tissue
LH triggers:
Ovulation
Development of corpus luteum
Secretion of progesterone
Oestrogen & Progesterone are the ovarian hormones.

19. Oestrogen Oestrogen stimulates:
Image source:
Oestrogen
Oestrogen stimulates:
cell division (proliferation) of the endometrium (inner layer of the uterus) allowing it to repair after menstruation.
the secretion of LH by the anterior pituitary

20. Progesterone Progesterone stimulates:
the thickening of the endometrium
inhibits the secretion of FSH & LH by the anterior pituitary

21. Effect of Hormones in females
GnRH = Gonadotrophin Releasing
Hormone

22. Menstrual Cycle 28 day cycle
Endometrium
Ovulation
Image source:
28 day cycle
each cycle continuous with previous cycle and next cycle
2 phases
View the animation on menstruation:
follicular phase
luteal phase

23. Menstrual Cycle: Follicular Phase
First half of cycle
FSH from pituitary stimulates development & maturation of a Graafian follicle and production of oestrogen from ovarian tissues
Repair & proliferation of the endometrium (due to increase in Oestrogen)
At day 14 - high Oestrogen levels cause a surge in the production of LH (& FSH) causing ovulation.

24. Ovulation Occurs on day 14
Surge in LH causes the wall of the Graafian follicle to rupture & release the egg
after ovulation the egg moves along the oviduct
for 3-4 days the egg can be fertilised if it meets a sperm
Ruptured follicle
Protective cells
Egg

25. Menstrual Cycle: Luteal Phase
Second half of cycle
LH stimulates Graafian follicle to become corpus luteum, which then secretes oestrogen & progesterone
Endometrium becomes thick, vascular & spongy, due to increase in progesterone, ready to accept & nourish the embryo if fertilisation has occured
FSH drops due to high oestrogen + progesterone so no new follicles LH
oestrogen
FSH

26. Menstrual Cycle: Luteal PhaseLH
oestrogen
FSH
Low LH causes degeneration of corpus luteum (day 22)
Followed by rapid drop in progesterone (& oestrogen)
If NO fertilisation, Menstruation begins at Day 28 because the ovarian hormones (oestrogen + progesterone) are so low that the endometrium can’t be maintained

27. Why do pregnant women not menstruate?
The fertilised egg secretes a hormone called human chorionic gonadotrophin (HCG) which maintains the corpus luteum which secretes progesterone preventing menstruation.
Image source: staff.um.edu.mt
After 6 weeks the placenta secretes progesterone instead.
Pregnancy tests, test for the presence of HCG in urine.

28. Image source: www.fertilityet.org.uk
to transport, nourish & filter sperm
Endometrium (food lining) develops
Endrometrium (+ some blood) is discharged
Role of cervix
The cells that line the cervix secrete mucus which lubricates the vagina.
High levels of oestrogen stimulate these cells to secrete a watery mucus which help sperm enter the reproductive tract.
High levels of progesterone cause the cervical mucus to thicken. During pregnancy this forms a semi-solid plug to protect the fertilised egg from infection.
Prostaglandins in the semen also help transport the sperm by inducing muscular contractions in the uterus & oviduct.

29. Body Temperature
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Body temperature rises by 0.5°C at ovulation and stays high during the luteal phase.
Changes in viscosity of cervical mucus & body temperature are used by some people as indicators for the rhythm method of birth control.

30. Continuous v Cyclical Fertility
Male fertility is continuous because they secrete a steady level of testosterone and produce a steady quantity of sperm.
Female fertility is cyclical due to the delicate balance of gonadotrophic and ovarian hormones. Females are usually only fertile for 3-4 days immediately after ovulation.