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Hormones & Sexual Development Lecture 25
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Sex, & Gender n Sex l biological differences l male & female l intersex n Gender l self-identity about sex role l may or may not match sex l heterosexual, homosexual, trans-gendered ~
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Hormones n Chemical messengers n Organizational l development l critical (sensitive) periods l permanent changes n Activational l control behavior & physiological processes l temporary ~
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Sex Hormones n Steroids l derived from cholesterol n Estrogens l estradiol n Androgens l testosterone (T) l dihydrotestosterone (DHT) ~
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Testosterone Dihydro- testosterone Estradiol 5- - reductase aromatase
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Sexual Differentiation n Sexually dimorphic n Genotypic sex l sex genes n Phenotypic sex l expression of genes ~
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Sexual Differentiation n Single gene n S ex-Determining R egion on the Y Chromosome l SRY n Testis Determining Factor (TDF) ~
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Development of Reproductive Organs
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Primordial Gonad n Indifferent gonad l first 6 weeks n No TDF ovaries l cortex n TDF testes l medulla ~
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Internal Reproductive Ducts n Müllerian system l female n Wolffian system l male n 3d month l 1 set withers n TDF testes l testosterone l Müllerian Inhibiting Hormone - MIH ~
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External Genitalia n Dihydrotestosterone n M/F same primordial tissue ~
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Sexual Differentiation of the Brain n Rats n Hypothalamus l Sexually Dimorphic Nucleus (SDN) n Spinal Cord l Spinal Nucleus of the Bulbocavernosus (SNB) ~
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Masculinization of Brain n Gonadotropin release patterns l Female: cyclical l Male: steady n Brain masculinized by... l testosterone? n Aromatase converts T estradiol l inside neurons ~
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Secondary sex characteristics n Puberty l Increased M/F sex hormone activity n Secondary characteristics l maturation of genitals l breasts l body shape n Pubic & axillary hair l females- androstenedione from adrenal glands ~
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Sexual Development Syndromes
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Congenital Adrenal Hyperplasia n Genotype: XX n Prenatal adrenal cortex hyperactivity l high levels of androgens l partially masculinized external genitalia ~
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Androgen Insensitivity Syndrome n Genotype: XY l No androgen receptors l Genetic mutation - X chromosome n Female body, brain, & gender identity l functional testes ~
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5- - Reductase Syndrome n Genotype: XY Fetal 5 - - reductase deficiency l no dihydrotestosterone l genitalia not masculinized n Rare l except Dominican Republic l 1:90 ~
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At puberty n Undescended testes functional 5- -reductase present: T DHT n Normal male development l Functioning penis develops ~
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What Determines Sex? n Interaction of… l genes l hormones l during critical periods n Sexual differentiation of… l body l brain ~
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