Trigone of the urinary bladder

Trigone of the Urinary Bladder

Diagram of the human bladder

The trigone of the urinary bladder is a smooth triangular region of the internal urinary bladder. It is defined by three points: the two ureteric orifices and the internal urethral orifice. This area is clinically significant due to its embryological origin and its role in urinary tract infections.

Anatomy

The trigone is located on the posterior wall of the bladder. It is a smooth area, unlike the rest of the bladder, which is lined with rugae that allow for expansion. The trigone is formed by the two ureteric orifices at the base of the bladder and the internal urethral orifice at the apex of the triangle.

The ureters enter the bladder obliquely, creating a one-way valve that prevents the backflow of urine. This is crucial for maintaining the sterility of the upper urinary tract. The internal urethral orifice is the opening through which urine exits the bladder into the urethra.

Embryology

The trigone is unique in that it is derived from the mesonephric ducts, whereas the rest of the bladder is derived from the urogenital sinus. This difference in embryological origin is significant because it influences the histological characteristics of the trigone, making it distinct from the rest of the bladder.

Clinical Significance

The trigone is clinically important for several reasons. It is a common site for the development of urinary tract infections (UTIs) due to its smooth surface, which allows bacteria to adhere more easily than the rest of the bladder. Additionally, the trigone is often involved in conditions such as interstitial cystitis and bladder cancer.

In males, the trigone is closely associated with the prostate gland, and conditions affecting the prostate can impact the function of the trigone and the bladder as a whole.

Pathology

Diagram showing the trigone of the bladder

Pathological conditions affecting the trigone include vesicoureteral reflux, where urine flows backward from the bladder into the ureters, increasing the risk of kidney infections. This condition is often due to a malfunction of the ureterovesical junction, which is part of the trigone.

Bladder stones and tumors can also affect the trigone, leading to symptoms such as hematuria, dysuria, and urinary frequency. The smooth nature of the trigone makes it a common site for the formation of bladder tumors.

Related Pages

• Urinary bladder
• Ureter
• Urethra
• Urinary tract infection
• Bladder cancer