Ch15: Sex Organs & Hormonal Control Higher Human Biology

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 hormonetestosterone

3. Sperm duct 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.

4. Sperm forming by meiosis

5. Pathway of sperm

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

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

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

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

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. Image source: www.hw.ac.uk

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. Image source: www.beliefnet.com 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 • inhibitsthe secretion of FSH & LH by the anterior pituitary

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

22. Menstrual Cycle Ovulation Endometrium follicular phase luteal phase Image source: www.medicine4faith.net • 28 day cycle • each cycle continuous with previous cycle and next cycle • 2 phases View the animation on menstruation: http://resources.schoolscience.co.uk/abpi/new/resources/hormones/horm4.asp

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. Ruptured follicle Protective cells Egg 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

25. FSH LH oestrogen 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

26. FSH LH oestrogen Menstrual Cycle: Luteal Phase • 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. Image source: staff.um.edu.mt 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. After 6 weeks the placenta secretes progesterone instead. Pregnancy tests, test for the presence of HCG in urine.

28. to transport, nourish & filter sperm Endometrium (food lining) develops Endrometrium (+ some blood) is discharged Image source: www.fertilityet.org.uk 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. Image source: http://en.wikipedia.org Body Temperature 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.