Reproduction

Reproduction - Chapter 22 Reproduction Sex Hormones Testes:...

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Chapter 22 Reproduction Sex Hormones Testes: androgens Ovaries: estrogens and progesterone Although males have more androgens and females have more estrogens and progesterone, all these hormones are found in both sexes Progesterone in men forms aldosterone. Adrenal cortex also produces sex hormones Events Following Fertilization Copulation = act of mating Sperm deposited into female to fertilize ovum After fertilization = pregnancy or gestation First two months: embryo After two months fetus About nine months: parturition or birth Role of Chromosomes in Determining Sex Chromosomes determine whether fetus develops ovaries or testes = sex determination Y chromosome: srY gene (sex-determining region on Y) If srY gene present –testes If srY gene absent – ovaries Females are the default sex Ovaries do not depend on estrogen, they develop in the absence of testosterone. Sex Differentiation Sex differentiation controlled by hormones First 40 days embryo sexually indifferent Wolffian ducts (precursor to male tract) Mullerian ducts (precursor to female tract) Sex Differentiation If testes present (due to srY gene), testes secrete: Testosterone Mullerian-inhibiting substance (MIS) These hormones stimulate development of wolffian ducts and degeneration of Mullerian ducts No testes (no srY gene), Hormones absent wollfian regress, Mullerian ducts develop- at 5 months Development of Reproductive Organs fig 22.2 Notice that the ovaries are not connected to the fallopian tubes. Sex Determination and Differentiation fig 22.3 MALE FEMALE Urogenital sinus prostate vagina Genital tubercle penis clitoris Labio folds scrotum labia Ducts vas deferens oviducts Gonads testes ovaries Errors in sexual development Testicular Feminization
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Androgen Insensitivity Syndrome No cell receptors for testosterone Clinical features: o XY embryo that ends up with external female genitalia o Internally have testes, no uterus or fallopian tubes o At puberty, testosterone is converted to estrogen for secondary sex characteristics Patterns of Reproductive Activity Over the Human Life Span Adolescence (up to 10-14 years): Inability to reproduce Puberty (starts at 10-14 years, later in boys): Sexual maturation Reproductive organs mature (can produce sperm) Secondary sexual characteristics develop Sexual maturation: (late teens on up) Female reproductive system cycles Female lose ability to reproduce around 45-50 Male can continually produce sperm Male Reproductive System fig 22.4 Testes need to be outside the body to stay cool Testes fig 22.5a Male gonads Seminiferous tubules is where the sperm develop made of sertoli cells Sperm production Cells of the Testis fig 22.5b,c Leydig cells (interstitial cells) Secrete testosterone Sertoli cells (epithelial cells) Support sperm development Cells of the Testis
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This note was uploaded on 09/22/2009 for the course BIOL 2160 taught by Professor Kt during the Spring '08 term at LSU.

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Reproduction - Chapter 22 Reproduction Sex Hormones Testes:...

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