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BioSciences Q. If it takes only one sperm to fertilise an egg, why do we need millions of sperm in an ejaculate ? A. The sperm won’t stop to ask for directions.

BioSciences I think it may be – We’ve only just passed the tonsils. Is it much further to the Fallopian tube?

BioSciences Reproductive systems and hormones Professor Geoff Shaw Department of Zoology KLES5: Chapter 20; Chapter 28 esp gonads and HPG axis section pp , fig KLES4: Chapter 19; Chap 27, esp p , Fig 27.10

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BioSciences n n diploid- 2nhaploid- 1n individual germ stem cells zygote mitosis male female sperm n n n n n n n n 2n egg meiosis fertilization one cell Germ cell development All other cells of the body: Somatic cells The Sexual Life Cycle see KLES4 Fig 19.4 Fertilization mitosis

BioSciences mouse testis stained to show tubules inside What are the main functions of the testis?

BioSciences Testes sperm production –occurs in seminiferous tubules –controlled by Sertoli cells – spermatogenesis hormone production –testosterone steroid androgen –made by Leydig cells between tubules Testosterone

BioSciences Seminiferous tubule peritubular myoid cells Sertoli cell primary spermatocyte spermatogonium LUMEN spermatid secondary spermatocyte sperm

BioSciences Sperm KLES4 Fig 19.22a

Ovaries egg production –oogenesis –occurs in follicle –controlled by granulosa cells hormone production –oestradiol steroid - oestrogen made by granulosa cells in follicle –Progesterone steroid - progestin made by corpus luteum after ovulation progesterone oestradiol egg (oocyte) ovulation follicle CL

BioSciences Mouse female reproductive tract: microscope slide note the thick secretory lining of the uterus (endometrium), regulated by oestradiol and progesterone multiple corpora lutea (CL) in this species (why?) CL uterus oviduct ovary this section enlarged on previous slide CL

BioSciences Testis hormones - Testosterone Testosterone –acts via androgen receptor in cells –stimulates accessory sex organs (eg prostate and seminal vesicles) –modulates male-type behaviour Testosterone oestradiol dihydro-testosterone (DHT)

BioSciences Ovary hormones - oestradiol Oestradiol –acts via oestrogen receptors in cells –controls oviduct, uterus, cervix, vagina and other sex organs –promotes oestrus behaviour (mating) Oestradiol

BioSciences Ovary hormones - progesterone Progesterone –acts via progestin receptors in cells –controls oviduct, uterus, cervix, vagina and other sex organs –modulates effects of oestradiol Progesterone

Control of testis hypothalamo-pituitary-gonadal axis gonadotrophin releasing hormone (GnRH) from hypothalamus stimulates release of LH and FSH (the gonadotrophins) from the pituitary LH stimulates Testosterone production by testis FSH stimulates spermatogenesis testosterone inhibits GnRH secretion (negative feedback) LH FSH GnRH testosterone - hypothalamus pituitary brain other brain centres accessory sex organs and secondary sex characters relatively constant T  homeostatic control

Control of ovary (follicle growth) hypothalamo-pituitary-gonadal axis gonadotrophin releasing hormone (GnRH) from hypothalamus stimulates LH and FSH (the gonadotrophins) release from the pituitary FSH stimulates –follicle growth/oogenesis –oestradiol production oestradiol regulates GnRH (negative feedback) LH FSH GnRH oestradiol - hypothalamus pituitary brain other brain centres reproductive tract growing follicles

Control of ovary (ovulation) Large follicles  HIGH oestradiol HIGH E2  (+)ve feedback Surge of LH causes ovulation LH FSH GnRH oestradiol + hypothalamus pituitary brain reproductive tract preparation oestrous behaviour mature follicles/ ovulation

Control of ovary (after ovulation) ovulated follicle transforms to corpus luteum (corpora lutea) oestradiol production falls porgesterone production increases progesterone  negative feedback on FSH preventing follicle growth after about 2 weeks (human) CL regresses allowing increased FSH and follicle growth LH FSH GnRH progesterone - hypothalamus pituitary brain other brain centres Uterus (preparation for pregnancy) corpora lutea

BioSciences menstrual cycle hormones see KLES5:Fig (uterine lining) switch to positive feedback

BioSciences Contraception Combined oral contraceptive pill –progestin plus oestrogen –suppresses GnRH  ↓ FSH and LH –prevents follicle growth and ovulation LH FSH GnRH oestradiol - hypothalamus pituitary brain reproductive tract Progestin/ oestrogen

BioSciences A male contraceptive pill? see KLES4 Box 19.2

BioSciences Tubal Ligation Vasectomy From: Life, Purves et al., 6 th Ed Ch.42 Animal Reproduction Methods of Contraception

Contraceptive effectiveness MethodMechanism % of women getting pregnant within 1 year Typical usePerfect use No method 85 Spermicideskill sperm2918 “rhythm method”abstinence near time of ovulation3515 condom (male)prevents sperm entering vagina152 contraceptive pillprevent ovulation80.3 implanonprevents ovulation0.05 IUDprevents embryo implantation vasectomyprevents release of sperm tubal ligationprevents egg from entering uterus

BioSciences 2 nd Year ZOOLOGY: Further Studies Physiological Aspects Animal structure and function Comparative Animal Physiology Comparative Animal Physiology Concepts in Cell & Devel Biology 3 rd Year Research Project Developmental Biology Reproduction Sex: Science and Society (University breadth) Sex: Science and Society (University breadth)

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BioSciences Next Lectures… Developmental Biology, Digestion, Feeding and Nutrition Dr Stephen Frankenberg

BioSciences What do I expect you to learn from this lecture? meiosis and the alternation of haloid and diploid generations structure and functions of the testis – sperm and testosterone stages of spermatogenesis and structure of mature sperm structure and function of the ovary – eggs, follicles (oestradiol), CL (progesterone) hypothalamo-pituitary control of testis and ovary hormonal control and the menstrual cycle contraceptives – mechanisms and efficiency

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HYPOTHALAMUS hypothalamus pituitary

PITUITARY hypothalamus pituitary

GONADS