The detrusor muscle is a layer of the urinary bladder wall counterfeit of smooth muscle Bladder Control fibers arranged in spiral, longitudinal, and circular bundles. When the bladder is stretched, this signals the parasympathetic high-strung system to convention the detrusor muscle. This encourages the bladder to expel urine through the urethra.

Here is a concise description of the urinary philosophy and the process of urination (micturition):