ANATOMY

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 primary function of the detrusor muscle is to contract during urination to push the urine out of the bladder and into the urethra. The detrusor muscle will relax to allow the storage of urine in the urinary bladder.

Detailed explanation-3: -The internal sphincter muscle is located at the opening of the bladder to the urethra. It is a smooth, involuntary muscle. Because of its location, it is also primary muscle prohibiting the release of urine. The external sphincter muscle surrounds the area of the urethra outside the bladder.

Detailed explanation-4: -Because the IUS is composed of smooth muscle, it is not under voluntary control. However, the IUS is controlled through the autonomic nervous system [17]. The IUS muscle controls the flow of urine by contracting around the internal urethral orifice.

Detailed explanation-5: -Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra.