females

• Teaching aims for females

  • The female reproductive system is much more complicated than the male reproductive system
  • The male produces sperm at a constant rate, whereas the female goes through a complicated cycle in which an egg matures and is released over the course of a month
  • The hormonal levels of the female fluctuate throughout her reproductive years until menopause
• Gonad development


  1. IF FEMALE: Gonad (cortex) forms ovary

  2. IF MALE: Gonad (cortex) regresses

  3. Bipotential stage (6 week fetus): Müllerian duct forms fallopian tube, uterus, cervix, and upper 1/2 of vagina (AMH absent)

  4. 10 weeks: Müllerian duct becomes fallopian tube, uterus, cervix, and upper 1/2 of vagina (AMH absent)

  5. At birth: Müllerian duct regresses (AMH present)
• Testosterone from testis converts Wolffian duct into seminal vesicle, vas deferens, and epididymis


  DHT controls prostate development
• Internal reproductive structures


  • Mammary glands
  • Fimbriae
  • Uterus
  • Cervix
  • Vagina
  • Cervical canal
  • Ovary
  • Uterine cavity
  • Fallopian tube
• Germ cells first duplicate themselves through mitosis. Then, through meiosis, they form gametes with one chromosome from each pair
• This photograph shows the tremendous difference in the sizes of human sperm and egg
• 46 chromosomes per cell (only two shown here)
• DNA replicates but no cell division
• Fertilization


  Zygote formation
• Ovary


  Produces female sex hormones and female germ cells
• Hormonal control of reproduction

  • Brain controls reproduction through GnRH and pituitary gonadotropins (FSH and LH)
• Feedback effects of sex steroids on gonadotropin release

  • Low estrogen or androgen
  • Moderate estrogen or androgen
  • High androgen
  • Sustained high estrogen
• Menstrual cycle


  Divided into phases based on events in the ovary (ovarian cycle) and in the uterus (uterine cycle)
• Phases of the ovarian cycle

  1. Follicular phase

  2. Ovulation

  3. Luteal phase
• Phases of the uterine cycle

  1. Menses

  2. Proliferative phase

  3. Secretory phase
• Hormonal control of the menstrual cycle

  Regulation of estrogen, inhibin, progesterone, FSH, and LH levels throughout the cycle
• Early to mid-follicular phase


  Estrogen and inhibin levels rise, FSH is suppressed
• Late follicular phase and ovulation

  Rising estrogen and progesterone cause the LH surge, FSH is suppressed by inhibin
• Early to mid-luteal phase


  Combined estrogen and progesterone shut off FSH and LH
• Late luteal phase


  Estrogen and progesterone fall when corpus luteum dies, gonadotropins start follicular development for a new cycle
• Follicular development for a new cycle

  1. GnRH

  2. Pituitary

  3. Hypothalamus

  4. FSH

  5. LH

  6. Follicle

  7. Granulosa cells

  8. Thecal cells

  9. Estrogens

  10. AMH

  11. Androgens

  12. Inhibin

  13. High estrogen output

  14. Small amount of progesterone

  15. Corpus luteum (from ovulated follicle)

  16. New follicles begin to develop

  17. Corpus luteum dies

  18. Estrogen and progesterone

  19. Inhibin secretes

  20. Tonic secretion resumes
• Ovarian steroid hormones


  • Estrogens
  • Progestagens
  • Androgens
• Actions of estrogen


  • Mediated by the estrogen receptor (ER), a dimeric nuclear protein that binds to DNA and controls gene expression
  • The estrogen:ER complex binds to specific DNA sequences called a hormone response element to activate the transcription of target genes
• Estrogens play a major role in growth, development, metabolism, and reproduction
• Fertilization process involves the secretion of HUMAN CHORIONIC GONADOTROPIN (hCG) by the chorionic portion (placenta)
• hCG prevents corpus luteum from degenerating, maintaining the secretion of PROGESTERONE AND ESTROGEN, which helps in maintaining the integrity of the uterine wall and inhibiting subsequent ovulation
• Birth-control pills mimic high estrogen/progesterone levels to inhibit ovulation by tricking the body into thinking it is pregnant
• After fertilization, hCG structurally similar to LH supports corpus luteum until the placenta produces sufficient amounts of progesterone
• Placental lactogen (hPL) breaks down fats from the mother to provide fuel for the growing baby, leading to insulin resistance and carbohydrate intolerance in the mother
• Placental hormones maintain pregnancy and support mammary gland development for milk production
• Placental hormones maintain pregnancy
• Mammary gland development purpose is production and ejection of milk
• Mammary gland development


  • Modified sweat glands present in both sexes
  • Functional only in females in response to prolactin
  • Alveoli cells secrete the milk and are clustered in lobules
• Lactation


  Prolactin and oxytocin are involved
• Production of oxytocin and its receptors


  Stimulated by estrogens and inhibited by progesterone
• In childhood: HPA remains highly sensitive to (-) feedback effects of gonadal steroids
• In puberty: adrenarche, decreased sensitivity of HPA to (-) feedback and gonadarche, increased E2, onset of ovulatory cycles
• Androstenedione, DHEA, DHEAS: 6-8 years
• Pulsatile secretion of GnRH is critical in the initiation of puberty
• In girls FSH increases earlier than LH