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Which came first - the chicken or the egg? Physiology of Reproduction

Which came first - the chicken or the egg? Physiology of Reproduction. Jennifer McDonald DO. Hypothalamic Pituitary Axis. Neural control. Chemical control. Dopamine (-). Norepiniphrine (+). Endorphins (-). Hypothalamus. Gn-RH. ?. ±. –. Ant . pituitary. FSH, LH. Ovaries.

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Which came first - the chicken or the egg? Physiology of Reproduction

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  1. Which came first - the chicken or the egg?Physiology of Reproduction Jennifer McDonald DO

  2. Hypothalamic Pituitary Axis Neural control Chemical control Dopamine (-) Norepiniphrine (+) Endorphins (-) Hypothalamus Gn-RH ? ± – Ant. pituitary FSH, LH Ovaries Estrogen Progesterone Uterus Menses

  3. Sequence of Maturation

  4. Telarche = breast development Estrogen dominant

  5. Tanner Staging - Breast Development Prepubertal Breast bud with areola widening

  6. Enlargement of breast. No separation of contours Secondary mound with separation of contours Mature breast

  7. Adrenarche = pubic hair growth Adrenal androgen dominant DHEA DHEAS

  8. Tanner Staging - Hair Growth Increased quantity, female triangle No hair Straight along labia

  9. More dense, curled, adult distribution Medial aspect of thighs

  10. Timing is Everything

  11. Menarche = onset of menses Average 2 to 2.5 years after breast development Average American girls 12.7 years +/- 1 year Earlier in African American and Hispanic girls Usually delayed until critical mass ~105 pounds or body fat content of 22%

  12. Delayed Puberty • No pubertal development by age 13 • Pubertal maturation not completed within 4 years or • Menses not begun by age 16

  13. Precocious Puberty • Breast or pubic hair development before 7 years (Caucasians) or younger than 6 years (African Americans) • Most common cause = idiopathic

  14. Menarche Requirements: • GnRH from the hypothalamus • FSH and LH from the pituitary • Estrogen and progesterone from the ovaries • Normal outflow tract

  15. Ovary Follicular Phase Ovulation Luteal Phase Uterus Proliferative Phase Secretory Phase Who’s Doing What

  16. Mature Ovary Non-growing = primordial follicles Growing follicles Primordial follicles are arrested in which stage of meiosis?

  17. Numbers Game 15 to 20 weeks gestation as many as 7 million germs cells in each ovary Newborn = 2 million primary oocytes Puberty = 300,000 primary oocytes remain 400 will become secondary oocytes and ovulate during reproductive years

  18. GnRH Gonadotropin releasing hormone Comes from ?? Stimulates ?? What is unique about its release ??

  19. Follicle Stimulating Hormone (FSH) Comes from ?? Release stimulated by ?? • Stimulates growth and maturation of follicles • Stimulates estrogen production in granulosa cells • Inhibited by estrogen and progesterone

  20. Theca interna - androstenedione in response to LH Granulosa cells - convert androstenedione to estradiol when stimulated by FSH

  21. Luetenizing Hormone (LH) Comes from ?? Release stimulated by ?? • Also stimulated by high levels of estrogen • Inhibited by estrogen & progesterone together • Triggers ovulation • Maintains the corpus luteum • LH surge initiates continuation of meiosis

  22. Ovulation occurs approximately 10-12 hours after the LH surge and 24-36 hours after peak estradiol levels attained

  23. Corpus Luteum (“yellow body”) • Theca interna & granulosa cells • Directed by LH • Synthesizes estrogen and significant amounts of progesterone (40 mg/day) • Progesterone causes secretory endometrium in preparation for implantation

  24. Indicators of Ovulation Prospective or retrospective? • Basal body temperature • Urinary LH • Serum progesterone Ovum lives approximately 24 hours after it is released but is fertilizable less than half that time

  25. Uterine Cycle

  26. Proliferative Phase Estrogen dominates Parallels follicular phase of the ovary Growth of blood vessels, mucosa and glands Secretory Phase Progesterone dominant Parallels luteal phase Mucous producing Uterine Cycle

  27. Normal Menstruation • Predominantly arterial • Usual duration 3-5 days • 1 to 8 days still normal • Average flow 30 mL • More than 80 mL abnormal

  28. Cervical Changes • Estrogen - thins • Progesterone - thickens • Spinnbarkeit • Fern Patterns

  29. Breast Changes • Estrogen - proliferation of ducts • Progesterone - growth of lobules & alveoli Mastalgia = cyclic breast pain

  30. Estrogens • Estrone (E1) • 17-estradiol (E2) • Estriol (E3) Which organs/cells are responsible for production of estrogen? Granulosa cells, theca cells, corpus luteum, and the placenta

  31. Estrogens • 17-estradiol is the major secreted estrogen • Estradiol is the most potent • Estriol is the least potent • 2% of circulating estradiol is free

  32. Progesterone • Secreted in large amounts by the corpus luteum and the placenta • 2% free in circulation • Important intermediate in steroid biosynthesis pathway • Fluctuate widely during cycle What does progesterone do?

  33. Testosterone • Secreted by ovaries, adrenal cortex (small) and peripheral conversion androstendedione (half) • Follow Circadian rhythms What time of day is testosterone its highest?

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