THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The internal urethral sphincter regulates involuntary control of urine flow from the bladder to the urethra, and the external urethral sphincter provides voluntary control of urine flow from the bladder to the urethra.

Detailed explanation-2: -The internal sphincter is part of the inner surface of the canal; it is composed of concentric layers of circular muscle tissue and is not under voluntary control.

Detailed explanation-3: -The internal urethral sphincter is located at the junction of the urethra and the urinary bladder. It is made of smooth muscle, and is under autonomic or involuntary control. The more inferiorly located external urethral sphincter surrounds the membranous or intermediate part of the urethra.

Detailed explanation-4: -The internal urethral sphincter and the external urethral sphincter both provide muscle control for the flow of urine. The internal sphincter is involuntary. It surrounds the opening of the bladder to the urethra and relaxes to allow urine to pass. The external sphincter is voluntary.