What muscle is responsible for contraction of the urinary bladder during micturition?

Detrusor & Urethra

Explanation:

The major contractile muscle of the bladder is the detrusor. Urination involves either sustained contractions or short intermittent contractions of the detrusor along with contraction of the muscles in the urethra, the duct from the urinary bladder that conducts urine from the body.