Internal Sex Organ Development:

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Internal Sex Organ Development Wolffian and
Mullerian Duct Differ.
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7.13
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Wolffian Ducts

• Develop into Epididymis, Vas Deferens Seminal
  Vesicles
• Depend on testosterone for development
• In males T comes from Leydig cells in testis
• In females they regress due to lack of T

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Mullerian Ducts

• Develop into Fallopian tubes, uterus upper 1/3
  of vagina
• Develop in the absence of Anti-Mullerian Hormone
  (AMH)
• Males secrete AMH in Sertoli cells of testis
• Females dont secrete AMH, therefore Mullerian
  ducts develop

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External Genitalia Development

• Dihydrotestosterone (DHT) stimulates penis and
  scrotum development in male
• Clitoris, labia, outer 2/3 of vagina develop in
  the absence of any hormone in females

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From Carlson Fig 10.5
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Summary

• Formation of male requires the presence of four
  factors
• TDF (from SRY gene)
• Anti-Mullerian Hormone
• Testosterone
• Dihydrotestosterone
• Formation of female occurs in absence of any of
  the above factors

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Congenital (Virilizing) Adrenal Hyperplasia

• Masculinization of female fetus in utero due to
  excess secretion of androgens.
• Female pseudohermaphrodite (ovaries normal but
  varying degrees of masculinization of genitalia)
• Typically caused by adrenal enzyme deficiency.
  Results in high levels of weak androgens

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Androgen Insensitivity Syndrome

• Mutation in Androgen Hormone Receptor
• Testes present (abdominal)
• Neither male nor female internal sex organs
• Phenotypically (externally) female
• Short vagina ends in cul-de-sac
• Behaviorally Female

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Androgen Insensitivity Syndrome
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Sexual Differentiation of the Hypothalamus

• Hypothalamus (preoptic area) controls pattern of
  hormone secretion in rodents
• POA is differentiated as male or female during
  critical period.
• Last 3 days of fetal development until postnatal
  day 10
• Exposure to T during critical period induces POA
  to become male brain

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Sexual Differentiation of the Rat Brain
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Sexually Dimorphic Nucleus of the Preoptic Area
Male
Female
5-7 times larger in male rats than female
rats. Dependent upon hormones during sensitive
period.
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