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Chapter 17: Reproduction A: Sex determination & differentiation B: Male reproductive physiology

Chapter 17: Reproduction A: Sex determination & differentiation B: Male reproductive physiology C: Female reproductive physiology. A “tripartite chain” of hormonal communication regulates reproduction:. The hypothalamus is part of the brain, so it is influenced

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Chapter 17: Reproduction A: Sex determination & differentiation B: Male reproductive physiology

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  1. Chapter 17: Reproduction A: Sex determination & differentiation B: Male reproductive physiology C: Female reproductive physiology

  2. A “tripartite chain” of hormonal communication regulates reproduction: The hypothalamus is part of the brain, so it is influenced by remarkably diverse inputs. The hormonal secretions of the anterior pituitary gland are stimulatory, tropic signals. The gonads synthesize steroid hormones and release the gametes.

  3. A: Sex determination & differentiation 1- Sex determination: depends on X and Y chromosomes. 2- Sex differentiation: (Fig 17-3) Male: SRY gene on Y- chromosome: Primordial gonads differentiate to testes Female: No SRY gene: Primordial gonads differentiate to ovaries

  4. Male Development

  5. Female Development

  6. B: Male reproductive physiology Figure 17-4 Cross section of testes

  7. Figure 17-11 Hormonal control of male reproductive physiology The “tripartite chain” regulates male reproduction: GnRH secretion from the hypothalamus drives LH & FSH secretion from the anterior pituitary gland. Testicular androgens exert diverse effects in the reproductive tract, including the promotion of spermatogenesis; these steroids and inhibin keep hormone levels in check as a result of negative feedback.

  8. C: Female reproductive physiology The full sequence of follicular maturation (3- 4 months) Figure 17-16

  9. Control of ovarian functions Figure 17-18 Ovulation is provoked by a surge in LH and marks the transition to the luteal phase of the cycle, characterized by high levels of progesterone. (8-14). Eventually, (15) a decrease in LH leads to luteolysis, and the withdrawal of steroid support for a thick, active uterus. Small increases in the secretion of gonadotropins (LH & FSH) lead to follicular maturation, including an increase in the synthesis and secretion of ovarian steroid hormones (1-7).

  10. The “tripartite chain” regulates reproduction: Figure 17-20 hormonal regulation of ovarian function: early & middle follicular phases: The cyclic pattern of GnRH secretion, which drives cyclic patterns of LH & FSH secretion, is driven by cyclic changes in the feedback relationship between the hypothalamus and the ovarian steroid hormones.

  11. Figure 17-21 hormonal regulation of ovarian function: late follicular phase: The feedback relationship between the ovarian steroid hormones and secretion from the hypothalamus/anterior pituitary gland reverses in mid-cycle, eliciting the large, ovulatory surge in LH.

  12. Thank you,,,

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