The external urethral sphincter muscle is a component of the urinary system that helps maintain bladder control by regulating urine flow and preventing involuntary leakage. Understanding its structure and function is important for understanding urination.
Where It Is Located
The external urethral sphincter muscle is part of the pelvic floor musculature, a group of muscles that support the pelvic organs. In males, it is located inferior to the prostate, at the level of the membranous urethra. In females, it is situated at the distal inferior end of the bladder within the deep perineal pouch.
This muscle is composed of skeletal muscle fibers, allowing for voluntary control over its contractions. This distinguishes it from the internal urethral sphincter, which is made of smooth muscle and operates involuntarily under the control of the autonomic nervous system. In females, the external sphincter is more complex, consisting of three parts that collectively encircle the urethra and, in some cases, the vagina.
How It Controls Urination
The primary function of the external urethral sphincter is to provide conscious control over urine flow. It achieves this by contracting to constrict the urethra, which prevents urine from leaving the bladder. This voluntary contraction is controlled by the somatic nervous system, specifically through the pudendal nerve, which transmits signals from the spinal cord to the muscle.
When a person decides to urinate, the external urethral sphincter relaxes, allowing urine to pass through the urethra. This coordinated relaxation, alongside the involuntary relaxation of the internal urethral sphincter and contraction of the bladder’s detrusor muscle, facilitates the emptying of the bladder. The external urethral sphincter is especially important in preventing urine leakage during activities that increase abdominal pressure, such as coughing, sneezing, or lifting heavy objects. Sensory feedback from the muscle to the central nervous system also helps in precise control over urination.
When It Doesn’t Work Properly
Dysfunction of the external urethral sphincter can lead to various urinary issues, including stress urinary incontinence (SUI) and overactive bladder (OAB). Stress urinary incontinence occurs when pressure inside the bladder exceeds the strength of the urethra to remain closed, leading to involuntary urine leakage during physical activities like coughing, sneezing, or exercising. This can happen if the pelvic floor muscles, including the external urethral sphincter, are weak or damaged.
Damage to the external urethral sphincter or surrounding nerves can result from various factors, such as childbirth or pelvic surgeries like hysterectomy or prostate removal. Neurological conditions affecting the brain and spinal cord, such as Parkinson’s disease or multiple sclerosis, can also disrupt the nerve signals to the sphincter, impairing its function. Overactive bladder, characterized by a sudden and frequent urge to urinate, sometimes with leakage, involves involuntary contractions of the bladder muscles, which can also be influenced by sphincter function.
Ways to Improve Its Function
Improving the function of the external urethral sphincter often involves strengthening the surrounding pelvic floor muscles. Kegel exercises are a common non-invasive method to achieve this. To perform Kegel exercises correctly, individuals should identify the pelvic floor muscles by imagining they are trying to stop the flow of urine or prevent passing gas. Once identified, these muscles are tightened, held for a few seconds and then relaxed for a similar duration.
It is recommended to perform multiple repetitions of these exercises, three to five times a day, across various positions like lying down, sitting, or standing. Consistency is important, with noticeable improvements observed within four to six weeks. Pelvic floor physical therapy, guided by a specialist, can provide personalized instruction and ensure proper technique. Additionally, lifestyle adjustments, such as maintaining a healthy weight and avoiding bladder irritants like caffeine and alcohol, can contribute to improved bladder control.