Expansion
A smooth triangular area between the two ureteric orifices and the internal urethral meatus
Expansion
- Bounded by the two ureteric orifices and the internal urethral orifice
- The superior boundary between the ureteric orifices is the interureteric ridge, a useful cystoscopic landmark for finding the orifices
- Its mucosa is smooth and firmly adherent to the underlying muscle, so it does not form rugae
The rest of the bladder derives from the urogenital sinus (endoderm), while the trigone derives from the absorbed mesonephric (Wolffian) ducts (mesoderm).
Clinically, the trigone is highly sensitive and is the region that generates the sensation of urgency, which is why a trigonal stone or catheter balloon causes such distress. It is also a common site for bladder carcinoma and for the inflammatory changes of chronic cystitis.