The urorectal septum is an invagination of the cloaca. It divides it into a dorsal part (the hindgut) and a ventral part (the urogenital sinus). It invaginates from cranial to caudal, formed from the endodermal cloaca, and fuses with the cloacal membrane. Malformations can cause fistulas.
Urorectal septum | |
---|---|
Details | |
Days | 32 |
Precursor | cloaca |
System | genitourinary system |
Identifiers | |
Latin | septum urorectale |
TE | septum_by_E5.4.9.0.2.0.14 E5.4.9.0.2.0.14 |
Anatomical terminology [edit on Wikidata] |
The urorectal septum is an embryonic structure formed from an invagination of the cloaca. The urorectal septum divides the cloaca into two parts:
The urorectal septum becomes part of the perineal body, helping to form the perineum.[1]
The urorectal septum develops from cranial to caudal, and is flat in the coronal plane.[1] It is formed from endoderm, the same germ layer as the cloaca. It fuses with the cloacal membrane.
Malformation of the urorectal septum can lead to several different types of fistulas.[2][3]
In women, at least five different types of fistula are possible.[3] All of these involve the fusion of the urogenital sinus and the end of the hindgut, causing the rectum to end in the vagina.[3] This may be associated with the uterus in the normal position, posterior to the hindgut, or bicornuate.[3]
In men, at least three different types of fistula are possible.[3] The hindgut may enter and preserve the urogenital sinus after birth.[3] The hindgut may replace the urogenital sinus completely, in which case it may also replace the urinary bladder and cause the ureters to drain into it.[3]
Urorectal septum malformation is associated with a number of other birth defects, including spina bifida, deafness, sacral hypoplasia, atrial septal defect, ventricular septal defect, tetralogy of Fallot, and limb musculoskeletal disorders.[3] Mainly because of these associations, up to 20% of children born with urorectal septum malformation may not survive long-term.[3] Outcomes from corrective surgery on a urorectal septum fistula are very good.[3]
This article incorporates text in the public domain from page 1109 of the 20th edition of Gray's Anatomy (1918)
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