NEET BIOLOGY

Detailed explanation-1: -A band of the detrusor muscle encircles this opening to form the internal urethral sphincter.

Detailed explanation-2: -The walls of the bladder are mainly formed by detrusor muscle, which allows the bladder to contract to excrete urine or relax to hold urine. At the inferior end of the bladder, the detrusor muscle is continuous with the internal urethral sphincter.

Detailed explanation-3: -The internal urinary sphincter is a continuation of the trigone/detrusor muscle which surrounds the bladder neck (2). When the bladder is filling, sympathetic innervation causes the internal sphincter to contract and close the bladder neck.

Detailed explanation-4: -The detrusor muscle is located within the walls of the bladder and is composed of smooth muscle fibers that are longitudinal and circular.