Lecture Tuesday September 11: UG embryology II

A. Male and Female Sexual Development

Male:
- SRY gene > differentiation of indifferent gonad to testis > Sertoli cells > Mullerian inhibiting substance > regression of Paramesonephric/Mullerian duct
- Leydig cells differentiate > testosterone > cause persistence of Mesonephric duct and tubules > rete testis and epididymis.

- seminal vesicles buds off distal mesonephric duct
- prostate buds off of urethra inferior to bladder

Female:
- No SRY > No Sertoli or Leydig cells > No MIS paramesonephric duct persists > uterus, cervix and Fallopian tubes.
- No testosterone so Mesonephric duct and tubules degenerate.
- Sinovaginal bulbs on the posterior aspect of the urogenital sinus gives rise to most of the vagina.

B. External Genitalia
Male:
Cells influenced by testosterone (5- alpha reductase converts to dihydrotestosterone)

Genital tubercle: glans of penis
Urogenital/urethral folds: shaft of penis and penile urethra
Genital swellings: scrotum
Hypospadias: ventral opening of the urethra failure of urethral folds to close completely

Female:
Genital tubercle: clitoris
Urogenital/urethral folds: Labia minora
Genital swellings: Labia majora

C. Descent of the testes
Processes vaginalis leads the way. The two layers fuse to form the tunica vaginalis. Failure of fusion can lead to indirect ing urinal hernia, hydrocele or testicular torsion.


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