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Development of the urinary bladder and Urethra Objectives Discuss the development of bladder, • ureter, and urethra. Describe the congenital anomalies of both • the urinary bladder and urethra. • The Cloaca is the dilatation of hind gut closed by The cloacal membrane • The Cloaca receives three openings: - The Alantois ventrally - 2 Mesonephric ducts one on each side Division of the cloaca -Occurs during 4th to 7th weeks - Urorectal septum , which is a mesodermal septum, divides cloaca into: 1-Primitive urogenital sinus anteriorly 2- Anorectal canal posteriorly After division of the cloaca, the anorectal • canal becomes continuous with the hindgut to form the Rectum and Anal canal Formation of primitive urogenital sinus & anorectal canal Division of cloacal membrane Urorectal septum divides the Cloacal membrane into: 1- The urogenital membrane anteriorly 2- The anal membrane Cloacal membrane urogenital membrane (anteriorly) anal membrane (posteriorly) Urogenital membrane Urorectal septum Anal membrane Division of the primitive urogenital sinus The entrance of the mesonephric ducts into the primitive urogenital sinus divides it into: 1- An upper part called the “vesico-urethral canal (3)” 2- A lower part called the “definitive urogenital sinus” which is subdivided into: A- A pelvic part (6) B- A phalic part (4) closed by the urogenital membrane Urorectal septum Cloaca Cloacal membrane Vesicouretheral canal Definitive Urogenital sinus Primitive Urogenital sinus Anorectal canal Pelvic part Phalic part Formation of the Trigone & migration of the Mesonephric ducts -The caudal parts of the mesonephric ducts are absorbed into the wall of the urinary bladder forming the trigone. - The mesonephric ducts migrate to open into future prostatic urethra leaving the ureters opening into lateral angles of the trigone 1- mesonephric duct 2-ureter 3-bladder trigone Migration of the mesonephric ducts to open into the prostatic urethra - The greater part of the urinary bladder develops from the vesico-rethral canal - The apical part develops from the proximal part of alantois - The distal part of the alantois is obliterated to form the median umbilical ligament ( Urachus) - The trigone develops from the absorbed caudal parts of mesonephric ducts • The mucosa of urinary bladder has double origin: 1.The trigone is mesodermal in origin develops from the lower parts of both mesonephric ducts. 2.The remaining part is endodermal in origin develops from the vesico-urethral canal (upper part of the primitive urogenital sinus). • The muscle of the urinary bladder is derived from the splanchnic mesoderm. Congenital anomalies of urinary bladder Urachal fistula, cyst & sinus -Allantois fails to obliterate -urine passes from the umbilicus -Localized area of the allantois persists -Secretory activity of epithelium results in cystic dilatation -Proximal part of alantois is obliterated and distal part persists. Serous fluid is discharged through umbilicus Ectopia vesica • The posterior wall of the urinary bladder is exposed to the exterior. • It is caused by the failure of the anterior abdominal wall and anterior wall of the bladder to develop. • It is due to inability of the mesoderm of the primitive streak to migrate around the cloacal membrane Development of the urethra in male -The Upper part of prostatic urethra develops from the vesicourethral canal -The Lower part of prostatic urethra and membranous urethra develop from the pelvic part of definitive urogenital sinus -The Penile urethra develops from the phalic part of definitive urogenital sinus • The Upper part from the vesicourethral canal • The Lower part from the pelvic part of the definitive urogenital sinus • From the pelvic part of the definitive urogenital sinus • From the phalic part of the definitive urogenital sinus • The surrounding connective tissue and smooth muscle tissue is derived from the splanchnic mesoderm Development of the urethra in female The female urethra develops from canal the vesicourethral • The female urethra develops from the vesicourethral canal • The surrounding connective tissue and smooth muscle tissue is derived from the splanchnic mesoderm Fate of the primitive urogenital sinus: A- Vesicouretheral canal: -1-Forms most of urinary bladder in both sexes. -2-Female urethera. -3-Upper ½ of prostatic urethera. N.B. Absorbed mesonephric ducts form: 1-Trigone of the bladder. -2-Back of female urethera. -3-Back of upper ½ of prostatic urethera. B- Pelvic part of the defenitive urogenital sinus: Forms the lower ½ of the prostatic urethera and the membranous urethera. C- Phalic part of the definitive urogenital sinus: - Forms the uretheral plate which is transformed into the uretheral canal that forms the penile urethera except in glans penis which is developed from cord of ectodermal cells which becomes canalized and communicates with rest of the urethera. CONGENITAL ANOMALIES OF URETHERA Epispadius: when the urethera opens into • the upper surface of penis. Hypospadius: when the urethera opens • into the lower surface of penis. Thank you