Physiology of the female reproductive system


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  • In the prepubertal state, the concentration of sex steroids and gonadotropins is low. The hypothalamic gonadostat is functional but highly sensitive to low levels of sex steroids,with the onset of puberty there is decreased sensitivity of the hypothalamus to negative feedback by sex steroids, increased release of LRF, and enhanced secretion of gonadotropins. In the negative feedback mechanism, the hypothalamus is less sensitive to feedback by sex steroids (adult set point) and adult levels of gonadotropins and sex steroids are present.
  • With rising estradiol production during the follicular phase of the cycle, the endometrial stroma thickens and the endometrial glands become elongated, this is a proliferative endometrium. The endometrium reaches a maximal thickness at the time of ovulation.
  • When ovulation occurs, the hormonal balance changes from an estrogenic state to a progestational state. P is not a mitogen, but causes differentiation of the tissues that contain p receptors. P converts the proliferative endometrium into a secretory endometrium. The endometrium stroma becomes loose and edematous, and blood vessels entering the endometrium become thickened and twisted. The endometrial glands, which were straight and tubular in the proliferative phase of the endometrium, become tortuous and contain secretory material within the lumina.
  • Physiology of the female reproductive system

    1. 1. Physiology of the Female Reproductive System
    2. 2. Physiological Stages <ul><li>Neonatal period: birth---4 weeks </li></ul><ul><li>Childhood: 4 weeks----12 years </li></ul><ul><li>Puberty: 12 years---18 years </li></ul><ul><li>Sexual maturation: 18 year---50 year </li></ul><ul><li>Perimenopause: decline of ovarian function (40 years)----1 year postmenopause </li></ul><ul><li>Postmenopause: </li></ul>
    3. 3. Menstruation <ul><li>Menstruation </li></ul><ul><li>cyclic endometrium sheds and bleeds due to cyclic ovulation </li></ul><ul><li>Mense </li></ul><ul><li>Endometrium is sloughed (progesterone withdrawal) </li></ul><ul><li>Nonclotting menstrual blood mainly comes from artery (75%) </li></ul><ul><li>Interval: 24-35 days (28 days). duration: 2-6 days. the first day of menstrual bleeding is consideredy by day 1 </li></ul><ul><li>Shedding: 30-50 ml </li></ul>
    4. 4. Central reproductive hormones <ul><li>Hypothalamus-Pituitary-Ovary(H-P-O axis) </li></ul>
    5. 5. Central reproductive hormones <ul><li>Neuroendocrine regulation </li></ul><ul><li>Gonadotropin-releasing hormone,GnRH </li></ul><ul><li>chemical structure </li></ul><ul><li>(pro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH 2 </li></ul><ul><li>Synthesize and transport </li></ul>nerve cells hypothalamus portal vein pitutary anterior lobe
    6. 6. Central reproductive hormones
    7. 7. Central reproductive hormones <ul><li>Regulation of GnRH </li></ul>Hypothalams GnRH Pituitary FSH, LH Ovary E,P
    8. 8. Central reproductive hormones <ul><li>Gonadotropins </li></ul><ul><li>Composition (glycoprotein) </li></ul><ul><li>Follicle stimulating hormone,FSH </li></ul><ul><li>Luteinizing hormone,LH </li></ul><ul><li>Synthesize and transport </li></ul>Gonadotroph (pulse) Blood circulation ovary
    9. 9. Central reproductive hormones <ul><li>Prolactin (PRL) </li></ul><ul><li>Regulated by the prolactin inhibiting factor (PIF) </li></ul>
    10. 10. The Ovarian cycle <ul><li>Function of ovary </li></ul><ul><li>Reproduction </li></ul><ul><li>development and maturation of follicle; ovulation </li></ul><ul><li>Endocrine </li></ul><ul><li>estrogens, progesterone, testosterone </li></ul>
    11. 11. The Ovarian cycle <ul><li>Cyclic changes of ovary </li></ul><ul><li>The development and maturation of follicle </li></ul><ul><li>Primordial follicle: before meiosis </li></ul><ul><li>Preantral follicle: zona pellucida, granulosa cells (FSH receptor) </li></ul><ul><li>Antral follicle: granulosa cells (LH receptor), E ↑ </li></ul><ul><li>Mature follicle: E↑,P↑ </li></ul><ul><li>Theca externa, theca interna, granulosa, follicular antrum, mound, radiate coronal </li></ul><ul><li>Follicular phase: day 1 to follicle mature (14 days) </li></ul>
    12. 12. The Ovarian cycle
    13. 13. The Ovarian cycle <ul><li>Ovulation </li></ul><ul><li>First meiosis completed -> collagen decomposed -> oocyte ovulated </li></ul><ul><li>Regulation </li></ul><ul><li>LH/FSH peak </li></ul><ul><li>E 2 ↑( mature follicle ) -> GnRH ↑ (hypothalamus) -> LH/FSH peak (positive feedback) </li></ul><ul><li>P cooperation </li></ul><ul><li>LH ↑ -> P ↑(follicle luteinized before ovulation) ->positive feedback </li></ul>
    14. 14. The Ovarian cycle <ul><li>Corpus luteum </li></ul><ul><li>follicle luteinized after ovulation: luteal cells </li></ul><ul><li>LH -> VEGF -> corpus hemorrhagicum </li></ul><ul><li>Regression </li></ul><ul><li>non fertilized -> corpus albicans </li></ul><ul><li>Luteal phase </li></ul><ul><li>Ovulation to day 1 </li></ul>
    15. 15. The Ovarian cycle <ul><li>sex hormones secreted by ovary </li></ul><ul><li>Composition </li></ul><ul><li>Estrogen, progesterone, testosterone </li></ul><ul><li>Chemical structure </li></ul><ul><li>Steroid hormone </li></ul><ul><li>Synthesis </li></ul><ul><li>Cholesterol->pregnenolone->androstenedione-> </li></ul><ul><li>testosterone->estradiol </li></ul><ul><li>Δ 5 or Δ 4 pathway of estrogen production </li></ul>
    16. 16. The Ovarian cycle <ul><li>Metabolism: liver </li></ul><ul><li>Cyclic change of E and P in ovary </li></ul><ul><li>Estrogen </li></ul><ul><li>E↑(day 7) -> E peak (pre-ovulate) -> E↓ -> E↑ (1 day after ovulate) ->E peak (day 7-8) -> E↓ </li></ul><ul><li>theca interna cells (LH receptor) -> testosterone </li></ul><ul><li>Granulosa (FSH receptor) -> estrogen </li></ul>
    17. 17. The Ovarian cycle <ul><li>Progesterone </li></ul><ul><li>P ↑ (after ovulation) -> P peak (day 7-8) -> P ↓ </li></ul>granulosa progesterone LH
    18. 18. Ovarian responses
    19. 19. The Ovarian cycle <ul><li>H-P-O axis </li></ul><ul><li>Positive feedback </li></ul><ul><li>Sex hormones (E) ↑ -> GnRH or LH/FSH ↑ </li></ul><ul><li>E peak ( ≥200pg/ml ) -> LH/FSH peak -> ovulation </li></ul><ul><li>Negative feedback </li></ul><ul><li>Sex hormones (E) ↑ -> GnRH or LH/FSH ↓ </li></ul><ul><li>Follicular phase: E ↑ -> FSH ↓ </li></ul><ul><li>Luteal phase: E ↑ P ↑ -> LH/FSH ↓ (formation) </li></ul><ul><li>E ↓ P ↓ -> LH/FSH ↑ (regression) </li></ul>
    20. 20. The endometral cycle <ul><li>Proliferative phase </li></ul><ul><li>E ↑ (mitogen) -> stroma thickens and glands become elongated -> proliferative endometrium </li></ul><ul><li>Duration: 2 weeks </li></ul><ul><li>Thickness: 0.5mm -> 5mm </li></ul>
    21. 21. The endometral cycle <ul><li>Secretory phase </li></ul><ul><li>P ↑ (differentiation) -> secretory endometrium </li></ul><ul><li>Features </li></ul><ul><li>stroma becomes loose and edematous </li></ul><ul><li>blood vessels entering the endometrium become thickened and twisted </li></ul><ul><li>glands become tortuous and contain secretory material within the lumina </li></ul><ul><li>Duration: 2 weeks </li></ul><ul><li>Thickness: 5-6mm </li></ul>
    22. 22. Change of Other genital organs <ul><li>Cervix </li></ul><ul><li>endocervical glands (E ↑ )-> mucus(thin,clear, watery) -> maximal (ovulation) </li></ul><ul><li>endocervical glands (P ↑ )-> mucus(thick, opaque, tenacious) </li></ul><ul><li>Vagina </li></ul><ul><li>Vaginal mucosa (E ↑) -> thickening and secretory changes </li></ul><ul><li>Vaginal mucosa (P ↑ ) -> secrete ↓ </li></ul>