{{Short description|Triangular region of the internal urinary bladder}} {{More citations needed|date=November 2016}} {{Infobox anatomy | Name = Trigone of urinary bladder | Latin = trigonum vesicae urinariae | Image = Bladder trigone.png | Caption = trigone of urinary bladder | Image2 = Gray1140.png | Caption2 = The interior of bladder. | System = }} The '''trigone of urinary bladder''' (also known as the '''vesical trigone''') is a smooth triangular region of the urinary bladder formed by the two ureteric orifices and the internal urethral orifice.<ref>{{Cite journal|last=Woodburne|first=Russell T.|date=1965-03-01|title=The Ureter, ureterovesical junction, and vesical trigone|journal=The Anatomical Record|language=en|volume=151|issue=3|pages=243–249|doi=10.1002/ar.1091510305|pmid=14324081|issn=1097-0185|url=https://deepblue.lib.umich.edu/bitstream/2027.42/49801/1/1091510305_ftp.pdf|hdl=2027.42/49801|hdl-access=free}}</ref> Between the ureteric openings, there is a fold of mucous membrane called the ''interureteric crest'' or ''Mercier bar''.<ref name="medical dict.">{{cite web |title=Mercier bar |url=https://medical-dictionary.thefreedictionary.com/Mercier+bar |website=TheFreeDictionary.com |access-date=29 May 2025 |language=en}}</ref> The trigone lies between the crest or ridge, and the neck of the bladder.<ref name="medscape2025">{{cite web |title=Trigonitis: Practice Essentials, Pathophysiology, Epidemiology |url=https://emedicine.medscape.com/article/438185-overview |access-date=30 May 2025 |date=12 February 2025}}</ref>
The area is very sensitive to expansion and once stretched to a certain degree, stretch receptors in the urinary bladder signal the brain of its need to empty. The signals become stronger as the bladder continues to fill.
Embryologically, the trigone of the bladder is derived from the caudal end of mesonephric ducts, which is of intermediate mesodermal origin (the rest of the bladder is endodermal). In the female the mesonephric ducts regress, causing the trigone to be less prominent, but still present.
==Clinical significance== The trigone can become irritated in a condition known as trigonitis resulting from long term use of a catheter, or from infection.<ref name="medscape2025"/>
==References== {{Reflist}}
==External links== * {{SUNYAnatomyLabs|44|04|02|03}} - "The Male Pelvis: The Urinary Bladder"
{{Urinary system}} {{Authority control}}
Category:Urinary system