Embryology and Hormones Flashcards
Types of sex
chromosomal, gonadal, phenotypic
Mutations in WT-1 gene (Wilms tumor) associated with
Gonadal dysgenesis, Wilms tumor, nephropathy
Mutations in SF-1 (Steroidogenic factor)
Regulates transcription of genes- deletions cause persistent muellarian system in males
SOX-9
Target of SRY; essential for normal testes development, and elevates AMH concentration with SF-1; deletions of mutations cause skeletal and gonadal dysgenesis
SRY region of short arm of Y chr
Produces testes-determining factor
5th week gestational age
Genital ridges overlay mesonephric ducts
6th week gestational age
primordial germ cells migrate from yolk sac to genital ridges (failure of migration results in streak gonads); primitive sex cords continue to proliferate
7th week gestational age
Gonads are undifferentiated and biopotential;
if male- SRY expression leads to differentiation, Sertoli cells make AMF (leading to Muellarian duct regression), seminiferous tubules and Leydig cells form, medullary cords mature into testis cords;
if female- in absence of y chr and SRY, the gonads develop into ovaries; DAX-1 and WNT-1 cause ovary differentiation, medullary cords degenerate in female
8th week gestational age
Lydia cells start to secrete testosterone
AMH
promotes regression of muellerian structures, produced by stroll cells, if not expressed before 8th week- no muellerian regression
Testosterone
promotes development of internal genetaliea, produced by leydig cells, regression if high levels of testosterone not present
Wolffian ducts become
Seminiferous Tubule
Ejaculatory Duct
Epididymis
Ductus Deferens
Female development
If no testes, then no AMH and no testosterone
Muellerian structures
Fallopian tubes
Midline uterus
Upper 1/3 of vagina
Internal genitalia
Testosterone (produced by leydig cells)
External genitalia
DHT (produced by converting T –> DHT; via alpha reductase)
Sertoli cells
secrete AMH/ MIF; lack of Sertoli cells cause internal male and female genitalia and externally male genitalia
DHT
Formed by enzyme 5 alpha reductase; lack of enzyme causes external female genitalia (until puberty when virilization occurs due increased testosterone levels which cross-react with DHT receptors)
Genital tubercle
penis/clitoris & corpus cavernosum-spongiosum/ vestibular bulbs
Urogenital sinus
Bulbourethral glands/ greater vestibular glands and prostate gland/Skenes’ glands
Urogenital folds
ventral shaft of penis/ labia minora
Labioscrotal swelling
scrotum/ labia majora
46, XX DSD (disorders of sexual differentiation)
Most commonly manifest as CAH; girls typically present with genital ambiguity, but have normal ovaries and uterus
46, XY DSD
Complete gonadal dysgenesis resuts in normal female external genitalia, normal female internal genitalia (b/c of lack of AMH and T), streak gonads