The Reproductive System

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The Reproductive System

• hypothalamus of the brain
• anterior pituitary gland
• gonads
• testes
• ovaries

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Major hormones

• brain gt gonadotropin-releasing hormone (GnRH)
• pituitary
• luteinizing hormone (LH)
• follicle-stimulating hormone (FSH)
• gonads
• androgens (males) dihydrotestosterone,
  testosterone, androstenedione
• estrogens (females) estradiol, estriol, estrone

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Male gonad testis

• made of lobules of seminiferous tubules
• tubules contain sperm cells, Sertoli (nurse
  cells)
• sertoli cells regulated by FSH
• tubules surrounded by Leydig cells
• Leydig cells produce testosterone
• LH regulates Leydig cell activity

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Female gonad ovary

• each egg housed in follicle
• follicle made of granulosa (nurse cells) and
  thecal cells
• thecal cells initiate production of estrogen
• theca makes androgens
• granulosa cells convert to estrogen
• FSH targets granulosa cells
• LH regulates thecal cells

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Think / pair / share

• Imagine you are a physician working in a
  fertility clinic. Your first patient of the day
  is a 35 year old male whose partner is fertile
  but they have been unable to conceive. After some
  lab work, you discover the following
• Your patient is azoospermic.
• Your patients testosterone levels are within
  normal range.
• Do you suspect that your patient is deficient in
  LH? In FSH? In GnRH? Provide a rationale for each
  of your answers.

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GnRH neurons

• fertility depends on GnRH secretion from brain
• Kallmans syndrome
• GnRH not secreted unless conditions are favorable
  for reproduction
• effects of stress, nutrition
• pattern of secretion
• GnRH analogs and infertility treatments

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Hypothalamic / pituitary connection

• median eminence
• hypophyseal portal vasculature
• general circulation

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Feedback systems

• reproductive hormone secretion regulated by
  steroid feedback
• steroids sex hormones (estrogen, testosterone)
• negative feedback gt slows down GnRH, LH and FSH
  pulse frequency
• positive feedback gt speeds up GnRH, LH and FSH
  pulse frequency

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