FATE OF CLOACA: • Uro-rectal septum divides the endodermal cloaca into: ventral primitive urogenital sinus and dorsal ano-rectal canal. • Primitive uro-genital sinus receives the openings of 3 ducts: 2 mesonephric ducts and allantois. • A constriction at the level of enterance of mesonephric ducts divides the sinus into 2 parts: • Cranial vesico-urethral canal. • Caudal defenitive uro-genital sinus.
DEVELOPMENT OF URINARY BLADDER • It develops from 3 parts: • Vesico-urethral canal (endodermal):forms most of the bladder. • Proximal part of allantois (endodermal):forms apex of the bladder, rest of allantois is called urachus. Later the urachus becomes obliterated to be median umbilical ligament. • Caudal parts of both mesonephric ducts: forms the trigone of the bladder.
CONGENITAL ANAMALIES • Ectopia Vesicae: due to failure of formation of anterior abdominal wall and anterior wall of urinary bladder. • Urachal Fistula: due to failure of obliteration of urachus. • Urachal Cyst: failure of obliteration of localized part of urachus. • Urachal Sinus: failure of obliteration of distal part of urachus.
DEVELOPMENT OF MALE AND FEMALE URETHERA • Female Urethra:is developed mostly from vesico-urethral canal (cranial part of primitive uro-genital sinus). • Male Urethera:Is composed of 3 parts: • Prostatic urethera: is developed from vesico-uretheral canal and absorbed mesonephric duct (upper 1/2) as well as pelvic part of defenitive uro-genital sinus (lower 1/2). 15 buds from the wall of urethera form the prostate gland by 12th week. • Membranous urethera: from pelvic part of defenitive uro-genital sinus. • Penile urethera: most of penile urethera is developed from phallic part of defenitive uro-genital sinus by the formation of uretheral plate then canal. Part of penile urethera in galns penis is developed from surface ectoderm. Two buds from proximal part of penile urethera will form bulbo-uretheral glands.
Fate of primitive urogenital sinus: A- Vesicouretheral canal: -Forms most of urinary bladder in both sex. -Female urethera. -Upper ½ of prostatic urethera. N.B. Absorbed mesonephric ducts forms -Trigone of the bladder. -Back of femal urethera. -Back of upper ½ of prostatic urethera.
B- Pelvic part of defenitive urogenital sinus: Forms lower ½ of prostatic urethera and membranous urethera. C- Phalic part of definitive urogenital sinus: - Forms uretheral plate which is transformed into uretheral canal that form the penile urethera except in glans penis which is developed from cord of ectodermal cells which becomes canalized and communicates with rest of urethera.
CONGENITAL ANOMALIES OF URETHERA • Epispadius: when urethera opens into the upper surface of penis. • Hypospadius: when urethera opens into lower surface of penis.