Talk:2009 BGD-B Lecture Sexual Differentiation: Difference between revisions

Revision as of 16:52, 27 May 2009

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

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 Tanner Stages
-Chromosomal
-Turner’s Syndrome
-Monosomy XO
-% non-viable embryos
-Fail to sexually mature at puberty
-Klinefelter’s Syndrome
-, XXY
-Begin normal male, become infertile
-Tall, mental dullness, behaviour problems
-Males
-, XX
-Develop as male, infertile adults
-Part of SRY gene located on one X
-Sex Reversal in Humans
-Hermaphroditism
-True
-,XX
-Gonads both ovary and teste tissues
-Ovotestes or ovary and testes
-Male Pseudohermaphrodites
-,XY
-Gonads of one sex, external genitalia of opposite
-Various causes
-Female Pseudohermaphrodites
-,XX
-Gonads are ovaries, external genitalia ambiguous
-Hyperplastic adrenals secrete androgens
-Gonadal Dysfunction
-Gonads fail to develop properly
-Gonadal Dysgenesis
-Swyer’s syndrome
-,XX
-Mixed Gonadal Dysgenesis
-,X/46,XY
-Primary Hypogonadism
-Affected females 46,XX
-Primary Hypogonadism
-Defective anterior pituitary production of gonadotropin
-Lack of gonadotropin-releasing hormone
-Tract Abnormalities
-Many different forms
-Uterine
-Associated with other anomalies
-Paramesonephric duct (0.1-0.5% of women)
-several classifications
-Unicornuate, bicornuate uterus
-Vagina
-Agenesis, atresia
-See also endocrine disruptors
-http://embryology.med.unsw.edu.au/Notes/endocrine2.htm
-Ductus Deferens
-Uni- or bilateral absence
-Failure of mesonephric duct to differentiate
-External Genitalia
-Multi-factoral
-Chromosomal, single gene, environmental
-Developmental arrest gives ambiguous
-Hypospadias
-Common male (1 in 300)
-failure of urogenital folds to fuse
-results in a proximally displaced urethral meatus
-Gonadal Descent
-Cryptorchidism
-One or both testes fail to descend into scrotum
-:30 live male births
-May be associated with other abnormalities
-Undescended Ovaries
-reasonably rare, also be associated with other uterine malformations (unicornuate uterus)
-Virilization of a Genetic Female with Ovaries
-Fetal androgens
-congenital adrenal hyperplasia (CAH)
-adrenal adenoma or hyperplasia
-Maternal androgens
-ovarian or adrenal tumors
-Latrogenic
-exogenous androgens or progestagens with androgenic activity
-Androgen Insensitivity Syndrome
-XY karyotype and presence of testes
-Externally
-develop female secondary sex characteristics
-Internally
-women lack Müllerian duct derivatives
-have undescended testes
 Sex and Brain Differentiation
 Brains of males and females differ