Male: differentiation of the urogenital sinus
In studies of the urinary system we have seen that the cloaca is subdivided by the uro-rectal septum into the rectum (dorsal) and the primary urogenital sinus (ventral).
The primitive urogenital sinus is in contact with the allantois. The upper part forms the future urinary bladder, while the middle and lower part forms the definitive urogenital sinus and, from it, the pelvic and phallic parts of the urethra (stage 17).
The pelvic part of the definitive urogenital sinus forms the prostatic and membranous parts of the urethra, the phallic part of the definitive urogenital sinus, the spongy part of the urethra and the urethral vestibule.
Around the 4th month an epithelial cord grows on the glans penis - into the depths - and binds it with the spongy part of the urethra.
From the mesonephric duct (Wolff) arise:
- Deferent duct
- Seminal vesicle
- Ejaculatory duct
From the endoderm of the urogenital sinus arise:
- Urinary bladder
- Out of the pelvic part of the definitive urogenital sinus: the prostatic and membranous parts of the urethra, the prostate and the bulbourethral gland (Cowper's).
- Out of the phallic part of the definitive urogenital sinus: the spongy part of the urethra and the urethral glands (Littre's)