hormones & sexual development lecture 23. sexual dimorphism n two forms l male and female n what...
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Hormones & Sexual
Development
Lecture 23
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Sexual Dimorphism
Two forms male and female
What determines your sex? ~
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Genetic determinants
XX or XY XO ?
Turner’s syndrome no ovaries
default = FEMALE MALE
Override genetic program ~
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Genotype complete genetic makeup
Phenotype expression of genes ~
Genotypic vs Phenotypic Sex
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Sexual Differentiation of Body
Chromosomal sex - XX or XY single gene
Sex-Determining Region on the Y Chromosome SRY ~
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SRY
Turns on switch testes development
XX + SRY? male
XY - SRY female ~
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Development of Reproductive Organs
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Primordial Gonad
Indifferent gonadPotential for both sexes
Medullatestes
Cortexovaries ~
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Differentiation
at 6 weeks SRY
medulla testes No SRY
cortex ovaries ~
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Internal Reproductive Ducts
< 6 weeks 2 sets
Müllerian system = female upper vagina uterus fallopian tubes ~
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Internal Reproductive Ducts
Wolffian system = male seminal vesicles vas deferens
3d month development 1 set withers
SRY testes testosterone Müllerian Inhibiting Hormone - MIH ~
Wolfian Müllerian
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Müllerian Inhibiting Hormone Testes scrotum develops Mullerian degenerates
Testosterone stimulates wolffian Testosterone to female
get both systems No MIH
Critical periods No MIH Mullerian ~
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External Genitalia
Dihydrotestosterone (DHT) critical period
testosterone ------------------------> DHT
5 - -reductase
M & F - same tissue ~
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Sexual Differentiation of the Brain
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Masculinization
Gonadotropin release patterns Female natural pattern
Brain masculinized by... testosterone? NO!ESTRADIOL
Structural differences? ~
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Sexual Dimorphism of the Brain
Hypothalamus Sexually Dimorphic Nucleus - SDN Spinal Nucleus of the
Bulbocavernosus ~
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testosterone -------------------> estradiol
aromatase
Aromatase present in neonates inject estradiol into neonate female
brain masculinized What protects females?
Rats - -fetoprotein Primates - placenta? ~
Masculinization of the Brain
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Secondary sex characteristics Puberty Increased M/F sex hormone activity
Secondary characteristics maturation of genitals breasts body shape
Pubic & axillary hair females- androstenedione from adrenal cortex ~
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Sexual Development Syndromes
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Adrenogenital Syndrome Congenital adrenal hyperplasia
genotype: XX prenatal adrenal cortex hyperactivity high levels of androgens
partially masculinized external genitalia ~
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Sex? Phenotype? Genotype?
Androgen Insensitivity Syndrome
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Androgen Insensitivity Syndrome Genotype: XY
No androgen receptors Genetic mutation - X chromosome gene
Born with vagina, raised as female Undescended testes become functional at
puberty. NOW WHAT HAPPENS?
Female body, brain, & gender identity
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5-alpha Reductase Syndrome
Genetically XY Fetal 5-alpha reductase
deficiency T not converted to DHT
Born with female external genitalia maybe raised as female
Dominican Republic 1:90 male births ~
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At puberty
Undescended testes become functional at puberty testosterone 5-a-reductase present converts T DHT
Development of male genitalia including penis secondary sex characteristics ~