Lecture 21 - Sexual Differentiation

Question 1

The bipotential fetus?

Answer 1

<6wk = bipotential gonads; 7wk = “” int. genitalia,; 8wk = “” ext.

Question 2

3 sections of bipotential gonad?

Answer 2

pronephros, mesonephros, metanephros

Question 3

Bipotential gonad formation?

Answer 3

yolk sac germ cells migrate down concentration gradient to join intermdiate mesoderm - aided by WT1 and SF1

Question 4

Development of male internal genitalia?

Answer 4

sertoli cells produce AMH -> Mullerian duct regression; Leydig cells produce testosterone -> Wolffian duct stabilisation - in absence of testes, Mullerian structures will remain leading to female int. genitalia

Question 5

Development of ext. genitalia?

Answer 5

becomes female if no androgen; 1st trimester placental HCG (and 2nd and 3rd LH and FSH) trigger testosterone Leydig cells to release testosterone -> DHT -> male external genitalia - lack of testosterone (androgen) leads to female ext. genitalia

Question 6

Gonadal determination?

Answer 6

SRY gene on Y chromosome that activates Sox-9, Sox-9 dublication can lead to male phenotype in XX

Question 7

Labia major and scrotum origin?

Answer 7

labioscrotal swelling

Question 8

Ambiguous Genitalia?

Answer 8

urgent karyotype (24hr rather than 3 month) and pelvic U.S. to identify uterus

Question 9

Virilized female?

Answer 9

ovaries, uterus, XX - prenatal androgen exposure

Question 10

Undervirilised Male?

Answer 10

testis, no uterus, XY - lack of prenatal androgen exposure or decreased testosterone sensitivity (LH mutation)

Question 11

WT1?

Answer 11

repressor and activating components @ gonadal ridge, also renal tumour suppressant

Question 12

SF1?

Answer 12

regulates development at gonadal, adrenal and pituitary development