Failure of the urorectal septum to fully divide the cloaca results in a persistent cloaca. The urorectal septum is formed by which embryonic process?

• A Proliferation of mesenchyme from the lateral plate mesoderm
• B Descent of endodermal folds from the cloacal membrane
• C Fusion of Rathke's plicae (lateral folds of endoderm) descending between allantois and hindgut ✓
• D Migration of neural crest cells into the hindgut

Explanation

The urorectal septum is formed by the fusion of Rathke's plicae — paired lateral ridges of endoderm (with mesodermal cores) that grow medially and caudally between the allantois anteriorly and the hindgut posteriorly. Their fusion creates the perineal body and divides the cloaca into the urogenital sinus anteriorly and the anorectal canal posteriorly. Failure leads to anorectal malformations (imperforate anus) or rectovesical/rectourethral/rectovaginal fistulae, depending on the level and degree of division failure.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.