Is trigone a part of the bladder?

No, the trigone is not a part of the bladder.

The trigone is a smooth, triangular area located on the posterior wall of the urinary bladder. It is formed by the convergence of the three ureteral orifices (openings of the ureters) and the internal urethral orifice (opening of the urethra).

Therefore, the trigone is a region within the urinary bladder. It is not considered a separate part of the bladder, but rather a specific anatomical feature of the bladder wall.