Talk:2009 BGD-B Lecture Sexual Differentiation

Development of the Genital System Dr Mark Hill Cell Biology Lab, SOMS Room G20 Wallace Wurth Bldg m.hill@unsw.edu.au UNSW Copyright Notice

Background Notes Fertilization Week 1 Gastrointestinal Tract Kidney Endocrine

Urinary Bladder - early

Endoderm Yolk sac, yolk stalk, gastrointestinal tract Hindgut Allantois extending into connecting stalk

Movie: Hindgut - Urogenital Sinus Urinary Bladder - Septation Cloaca divided (week 6) Urorectal septum Posterior- rectum Anterior- urogenital sinus Continuous with allantois Apex of developing bladder Urachus Median umbilical ligament

SRY on Gonad Development Gonad gastrulating mammalian embryo cells signaled by neighbours form primordial germ cells (pgc) migrate into genital ridges which develop into gonads Primordial germ cells develop into eggs, if gonad is becoming an ovary sperm, if gonad is becoming a testis Gonad will develop into an ovary unless its somatic cells contain a Y chromosome Carnegie stage 13/14 Kidney 3 Stage Development Pronephros, Mesonephros, Metanephros

Nephrons Movie: Germ Cell Migration Internal Genital Organs All embryos form paired Nephric duct Mesonephric duct (Wolffian) See kidney development Paramesonephric duct (Mullerian) Humans 7th week Invagination of coelomic epithelium Cord grows and terminates on urogenital sinus Male Gonad (testes) secretes Mullerian duct inhibitory factor (MDIF) Causes regression of paramesonephric duct Testosterone Retains mesonephric duct Female - opposite Movie: Germ Cell Migration Movie: Germ Cell Migration Movie: Germ Cell Migration SRY on Gonad Development Differentiation of Human Gonads Movie: Gonad Development Gonad Differentiation Overview Male Mesonephric Duct (st22) Movie: Bladder Fetal Testis Infant Ovary Infant Ovary Ovary - Germ Cell Numbers External Genitalia Internal Genital Tract Female - paramesonephric - uterus Male - mesonephric - ductus deferens External Genital Organs All embryos initially same (indifferent) Testosterone Differentiates male External Genital Organs External Genitalia Hormone Dependent Genitalia Male Hormone dependent anatomy Genital Ligaments Movie: Gonad Descent Both male and female gonads descend See also Abnormalities - Cryptorchidism

Puberty - Hormone Axis LH & FSH Difference in timing increased gonadotrophin secretion and stimulate gonadal maturation rise in testosterone and estradiol secretions in males and females respectively positive feedback of estradiol in females also occurs during puberty Tanner Stages - External Genitalia Tanner Stages - Mammary Tanner Stages

Sex and Brain Differentiation Brains of males and females differ regions specialized for reproduction Also in other regions (controlling cognition, etc) where sex differences are not necessarily expected Differentially susceptible to neurological and psychiatric disease 2 sources of sexually dimorphic information complement of sex chromosome genes mix of gonadal hormones sex differences in brain attributed to differential action of gonadal hormones evidence for sex chromosome effects on both neural and non-neural systems XX and XY cells differentiate even before they are influenced by gonadal hormones even if exposed to similar levels of gonadal steroids Hormone Axis - Reproduction Infections Infections