PATHOLOGY

Detailed explanation-1: -The trigone (a.k.a. vesical trigone) is a smooth triangular region of the internal urinary bladder formed by the two ureteric orifices and the internal urethral orifice.

Detailed explanation-2: -urinary bladder structure …of the bladder neck, or trigone, is demarcated by the two ureteric orifices and the internal opening of the urethra. Muscle fibres loop around the urethral opening to form the internal sphincter, which is under involuntary control.

Detailed explanation-3: -Cholinergic muscarinic (M2 and M3) receptors are distributed in the body of the bladder, trigone, bladder neck, and urethra. The M2 cholinergic muscarinic receptors structurally predominate in normal bladders, but the M3 receptors may be functionally more important for bladder contraction.