Internal urethral sphincter

Diagram of the male and female urethra. The internal urethral sphincter is not labeled but is located just below the bladder.

The Internal Urethral Sphincter is a muscular structure in the human body that plays a crucial role in the urinary system. It is located at the neck of the bladder, where the bladder connects to the urethra.

Anatomy

The internal urethral sphincter is a smooth muscle that forms a ring around the urethra. It is involuntary, meaning it operates without conscious control. This muscle is responsible for preventing the involuntary leakage of urine from the bladder into the urethra.

Function

The primary function of the internal urethral sphincter is to prevent the flow of urine from the bladder into the urethra until urination is appropriate. It does this by contracting and closing off the urethra. When it is time to urinate, signals from the brain cause the sphincter to relax, allowing urine to flow from the bladder, through the urethra, and out of the body.

Clinical Significance

Problems with the internal urethral sphincter can lead to urinary incontinence, a condition where an individual is unable to control their urine flow. This can be due to damage to the sphincter itself, or to the nerves that control it. Treatments for this condition can include medication, surgery, or the use of a catheter.

See Also

• Urinary system
• Urinary incontinence
• Urethra