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UNIT 2 – THE CONTINUATION OF LIFE

UNIT 2 – THE CONTINUATION OF LIFE. Chapter 15 – Sex Organs & Hormonal Control. Testes. Site of sperm & testosterone production Sperm made in the seminferous tubules (connected to sperm duct) Testosterone produced by insterstitial cells

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UNIT 2 – THE CONTINUATION OF LIFE

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  1. UNIT 2 – THE CONTINUATION OF LIFE Chapter 15 – Sex Organs & Hormonal Control

  2. Testes • Site of sperm & testosterone production • Sperm made in the seminferous tubules (connected to sperm duct) • Testosterone produced by insterstitial cells • Sperm need energy & a liquid medium (semen) to move • Seminal vesicles secrete liquid: • - Fructose • - for energy • - Prostaglandins • - stimulate female contractions • Prostate gland – secretes enzymes • - maintains semen viscosity • The seminal vesicles & prostate are accessory glands

  3. Ovaries • Site of egg production • Eggs contained in Graafian follicle • - secretes oestrogen • After ovulation, follicle develops into corpus luteum • - secretes progesterone

  4. Hormonal Control • Hormones – chemical messengers • Secreted by endocrine glands into bloodstream • Specific responses from target tissues • Pituitary: • Secretes gonadotrophic hormones • e.g • FSH (follicle stimulating hormone), • ICSH (Interstitial cell stimulating hormone) • LH (lutenising hormone)

  5. Influence of hormones - males • FSH promotes sperm production • ICSH (LH) stimulates testosterone production • Testosterone: • Stimulates sperm production • Also activates prostate & seminal vesicles • Testosterone self-regulates • - high conc. inhibits FSH & ICSH secretion • - low conc. FSH & ICSH secreted again • - this is negative feedback ICSH

  6. Influence of hormones - ovaries • FSH stimulates Graafian follicle development • - & oestrogen secretion • LH triggers ovulation • LH stimulates progesterone secretion

  7. Influence of hormones – uterus/pituitary • Oestrogen: • Stimulates proliferation of uterus lining (endometrium) • Stimulates LH secretion by pituitary • Progesterone: • Promotes endometrium thickening • Inhibits FSH & LH secretion

  8. Menstrual Cycle • Continuous cycle – 28 days long • Follicular Phase • FSH stimulates Graafian follicle • Endometrium proliferated ( by Oestrogen production) • Day 14 – LH production surge • Graafian follicle ruptured • Egg into oviduct – 3 to 4 days for fertilisation

  9. Menstrual Cycle • Luteal Phase: • Graafian follicle into corpus luteum • Progesterone rise = endometrial development • Pituitary inhibited (-ve feedback) – FSH/LH levels drop (no more ovulation) • Day 22 – corpus luteum degenerates • Progesterone & oestrogen levels drop • Day 28 – endometrium lost = menstruation

  10. Menstrual Cycle

  11. Fertilisation • If fertilised – egg secretes HCG (similar to LH) • Corpus Luteum maintained • Progesterone secreted continuously – endometrium thickened • Menstruation prevented • - at 6 weeks placenta controls progesterone production • Pregnancy tests detect HCG in urine

  12. Role of cervix • Cervix cells secrete mucus – lubrication of the vagina • Oestrogen stimulates watery mucus secretion • – easier sperm penetration • Sperm directed by molecules in mucus • Prostaglandins assist in muscular contractions • High levels of progesterone thickens mucus • – protects fertilised egg from infection

  13. Fertility • In males – FSH/ICSH at a constant level • Constant production of testosterone & sperm • Men are continuously fertile • In females – hormone levels alter greatly • Cyclical fertility – (3-4 days after ovulation) • Signs – temp increase (0.5oC) & watery mucus

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