Related Experiment Video
Updated: Aug 15, 2026

Surgical Management of Meatal Stenosis with Meatoplasty
Published on: November 30, 2010
Does the urorectal septum fuse with the cloacal membrane?
B Q Qi1, S W Beasley, A K Williams
1Department of Paediatric Surgery, Christchurch Hospital, Christchurch, New Zealand.
Purpose:
Traditional theories of cloacal embryogenesis assume that the urorectal septum fuses with the cloacal membrane before the anal membrane disintegrates. However, recent observations in humans and other species raise doubt about this assumption. We determined whether urorectal septum fusion occurs in rats.
Materials And Methods:
Rat embryos were harvested at specific times between days 11 and 16 of gestation. We evaluated the morphology, growth and relationship of the urorectal septum to the cloacal membrane on serial histological sections.
Results:
The urorectal septum consistently fused with the cloacal membrane on day 15 of gestation before the cloacal membrane began to disintegrate.
Conclusions:
In rats the urorectal septum fuses with the cloacal membrane, after which the urogenital membrane and anal membrane disintegrate by a process of apoptosis.
Related Concept Videos
Muscles of the Pelvic Floor and Perineum
Perineal Layer
The perineum is a diamond-shaped area below the pelvic diaphragm, divided into an anterior urogenital triangle that contains the external genitals and a posterior anal triangle housing the anus. The urogenital...
Ureters
Urinary Bladder
In males, the bladder is situated in front of the rectum, while in females, it is positioned anterior to the vagina and uterus. The bladder floor contains an inverted triangular area called the trigone, defined by the two ureteric...
The Micturition Reflex
The process begins with bladder filling, where the bladder wall stretches as urine accumulates. This stretching activates the urine storage reflex, mediated by the sacral spinal segments and the pontine storage center. Efferent sympathetic impulses stimulate the detrusor muscle to relax and the internal urethral sphincter to contract, facilitating urine...
Urethra
The anatomy of the urethra differs between males and females. In females, the urethra is short, measuring about 3–4 cm in length, and opens anterior to the vaginal opening. In males, the urethra is longer and passes through the penis, serving dual purposes: expelling urine and ejaculating semen. The male urethra is...
Anatomy of the Genitourinary System II: Bladder and Urethra

