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Bladder

Embryology

Reviewer: Alcides Chaux, M.D., Johns Hopkins University School of Medicine (see Reviewers page)
Revised: 19 April 2011, last major update April 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

General
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● Bladder develops during first 12 weeks of gestation
● Bladder and trigone development are regulated by complex epithelial-mesenchymal signaling events (Curr Opin Urol 2009;19:427)
● Urorectal septum divides cloaca into dorsal rectum and ventral urogenital sinus
● Urogenital sinus is further divided into 3 parts: cranial vesical part (forms most of bladder, except trigone), middle pelvic part (forms urethra in bladder neck, prostatic urethra in males, and entire urethra in female), and caudal phallic part (primordium of penis or clitoris)
● Trigone develops from dilation, fusion and incorporation of caudal mesonephric ducts into urogenital sinus, forming a triangular area that is site of future ureters
● Mesonephric ducts are gradually absorbed and replaced by endodermal epithelium of urogenital sinus
● Posterior walls, dome and part of lateral walls arise from mesenchyme surrounding urogenital sinus
● Anterior wall and part of lateral walls develop with closure of infraumbilical portion of abdominal wall
● Note: neither urachus or allantois are involved in formation of bladder

Micro description
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● Allantois: rudimentary structure lined by endoderm that is connected to urachus
● Urachus: formed during descent of abdominal wall, connects umbilicus to apex (dome) of bladder, torn apart as embryo elongates but remnants persist in anterior abdominal wall and may persist in bladder wall (see patent urachus)

Micro images
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Early fetal development

Diagrams
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Development of bladder


Cloacal septal formation (animation)

Additional references
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● Atlas of Human Embryology
● University of North South Wales

End of Bladder > Embryology

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