Logan Steele
The human body has two urethral sphincter muscles that control the exit of urine from the urinary bladder through the urethra. The two muscles are the internal urethral sphincter and the external urethral sphincter. The internal sphincter is involuntary and surrounds the opening of the bladder to the urethra. The external sphincter is voluntary and surrounds the urethra outside the bladder. Both muscles must be relaxed for urination to occur.
| Characteristics | Values |
|---|---|
| Name | Internal urethral sphincter and external urethral sphincter |
| Location | The internal sphincter is located at the bladder's inferior end and the urethra's proximal end at the junction of the urethra with the urinary bladder. The external sphincter surrounds the urethra outside the bladder. |
| Control | The internal sphincter is involuntary and is under autonomic control. The external sphincter is voluntary and is under somatic control. |
| Function | The internal sphincter controls involuntary urine flow from the bladder to the urethra, whereas the external sphincter controls voluntary urine flow. |
| Structure | The internal sphincter is a continuation of the detrusor muscle and is made of smooth muscle. The external sphincter is made of skeletal muscle. In males, the external sphincteric mechanism is more complex, as it correlates with fibres of the rectourethralis muscle and the levator ani muscle. In females, the external sphincter is made up of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae. |
Explore related products
What You'll Learn
The internal urethral sphincter controls involuntary urine flow
The internal urethral sphincter is a smooth muscle that controls involuntary urine flow from the bladder to the urethra. It is located at the bladder's inferior end and the urethra's proximal end, at the junction of the urethra with the urinary bladder. This muscle is a continuation of the detrusor muscle, which surrounds the bladder.
The internal urethral sphincter is responsible for prohibiting urination. It surrounds the opening of the bladder to the urethra and must relax to allow urine to pass. When the bladder is full, stretch receptors in the bladder wall trigger the micturition reflex, causing the detrusor muscle to contract and the internal urethral sphincter to relax, allowing urine to flow into the urethra. This process is involuntary, and the internal urethral sphincter is under autonomic control.
In contrast, the external urethral sphincter controls voluntary urine flow. It surrounds the urethra outside the bladder and must be relaxed for urination to occur. The external sphincter is made of skeletal muscle and is under the voluntary control of the somatic nervous system. In males, the external sphincteric mechanism is more complex, correlating with fibres of the rectourethralis and levator ani muscles.
Both the internal and external urethral sphincters function together to prevent the release of urine. Damage to either of these muscles can lead to urinary incontinence. Additionally, the internal urethral sphincter has a secondary function in males, which is to prevent the flow of semen into the bladder during ejaculation.
The process of micturition, or urination, involves the bladder expanding like an elastic sac to hold urine. As it reaches capacity, involuntary muscle movements send signals to the nervous system, triggering the decision to urinate. This process is under conscious control, and the brain signals the sphincter and pelvic floor muscles to relax, allowing urine to pass through the urethra.
Running for Muscle Gain: Is It Effective?
You may want to see also
Explore related products
The external urethral sphincter controls voluntary urine flow
The urethral sphincters are two muscles that control the exit of urine from the urinary bladder through the urethra. The two muscles are the internal urethral sphincter and the external urethral sphincter. When either of these muscles contracts, the urethra is sealed shut. The external urethral sphincter originates at the ischiopubic ramus and inserts into the intermeshing muscle fibres from the other side. It is controlled by the deep perineal branch of the pudendal nerve. Activity in the nerve fibres constricts the urethra.
The internal urethral sphincter controls involuntary urine flow from the bladder to the urethra. It is located at the bladder's inferior end and the urethra's proximal end at the junction of the urethra with the urinary bladder. The internal sphincter is a continuation of the detrusor muscle and is made of smooth muscle, therefore it is under involuntary or autonomic control. This is the primary muscle for prohibiting urination.
In females, the external sphincter muscle is more elaborate than in males as it is made up of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae. The urethrovaginal muscle fibres wrap around the vagina and urethra, and contraction leads to the constriction of both the vagina and the urethra. The origin of the compressor urethrae muscle is the right and left inferior pubic ramus, and it wraps anteriorly around the urethra so when it contracts, it squeezes the urethra against the vagina.
Weak pelvic floor muscles, intrinsic sphincter damage, or damage to the surrounding nerves and tissue can make the urethral sphincter incompetent, and subsequently, it will not close fully, leading to stress urinary incontinence.
Chest Muscle: Is It Big or Small?
You may want to see also
Explore related products
Pelvic floor muscles are essential for bladder control
The pelvic floor muscles play a crucial role in bladder control. These muscles, along with the urethral sphincters, work together to control the release of urine. The pelvic floor muscles support the bladder and urethra, while the urethral sphincters act as valves, opening and closing the urethra to allow urine to pass.
The internal and external urethral sphincters are the primary muscles responsible for controlling the exit of urine from the bladder through the urethra. The internal sphincter, located at the junction of the bladder and urethra, is made of smooth muscle and is under involuntary or autonomic control. It surrounds the opening of the bladder to the urethra and relaxes to allow urine to pass. This is the primary muscle for prohibiting urination.
The external sphincter, on the other hand, is a voluntary muscle that surrounds the urethra outside the bladder. It is made of skeletal muscle and is under the control of the somatic nervous system. For urination to occur, the external sphincter must relax. In women, the external sphincter is more elaborate, consisting of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae.
Weak pelvic floor muscles or damage to the urethral sphincters can lead to urinary incontinence, or the accidental loss of urine. This can be caused by various factors, including childbirth, obesity, age, prostate surgery, and radiation therapy. Pelvic floor muscles can be strengthened through Kegel exercises, which can improve bladder control. Additionally, maintaining a healthy weight and avoiding certain foods and drinks, such as caffeine and alcohol, can also contribute to better bladder control.
In summary, pelvic floor muscles are essential for maintaining bladder control by working in conjunction with the urethral sphincters to regulate urine flow. Any damage or weakness in these muscles can lead to urinary incontinence, highlighting the importance of maintaining their strength and function for overall urinary health.
Icing Muscle Injuries: Reducing Inflammation and Pain
You may want to see also
Explore related products
The detrusor muscle contracts during urination to release urine
The detrusor muscle is a smooth muscle found in the wall of the bladder. It is innervated by the autonomic nervous system and is under involuntary or autonomic control. The primary function of the detrusor muscle is to contract during urination to release urine from the bladder into the urethra.
The bladder is an elastic sac that holds urine. As it reaches its capacity, the process of micturition or urination begins. Involuntary muscle movements send signals to the nervous system, putting the decision to urinate under conscious control. When the bladder is full of urine, stretch receptors in the bladder wall trigger the micturition reflex. The detrusor muscle contracts and the internal urethral sphincter muscle relaxes, allowing urine to pass out of the bladder and into the urethra.
The internal urethral sphincter controls involuntary urine flow from the bladder to the urethra, while the external urethral sphincter controls voluntary urine flow. The internal sphincter is a continuation of the detrusor muscle and is made of smooth muscle. The external sphincter is made of skeletal muscle and is under voluntary control. Both sphincters function to prevent the release of urine. When either of these muscles contracts, the urethra is sealed shut.
In older adults over 60 years of age, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention. Detrusor muscle pathology can lead to urinary retention, incontinence, or a combination of both. Abnormalities of the detrusor muscle, if left untreated, can lead to deterioration of the upper urinary tracts.
Cycling's Muscle-Building Benefits: Which Muscles Does It Develop?
You may want to see also
Explore related products
Urinary incontinence can be caused by muscle damage
Urinary incontinence is the loss of bladder control, which causes involuntary urination. The internal urethral sphincter controls involuntary urine flow from the bladder to the urethra, while the external urethral sphincter controls voluntary urine flow. When these muscles contract, the urethra is sealed shut. However, any damage to these muscles can lead to urinary incontinence.
Stress incontinence is usually the result of weakened or damaged pelvic floor muscles and the urethral sphincter. In women, childbirth, obesity, and age can be risk factors for stress incontinence, while in men, prostate surgery and radiation therapy can damage the sphincter and cause stress incontinence. Urge incontinence can occur when the urethra cannot hold urine as the bladder contracts uncontrollably due to overactivity of the detrusor muscle. The detrusor muscle surrounds the bladder and contracts during urination to release urine. In older adults, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention.
Overflow incontinence is caused by an obstruction or blockage in the bladder, preventing it from emptying fully. Total incontinence may be caused by birth defects, spinal injuries, or a fistula. Certain factors can increase the risk of urinary incontinence, including obesity, and maintaining a healthy weight through exercise and a balanced diet may help reduce the chances of developing incontinence. Additionally, Kegel exercises can help strengthen the pelvic floor muscles and reduce the risk of incontinence.
Exploring the Bumpy Texture of Muscles
You may want to see also
Frequently asked questions
The internal and external urethral sphincters control the flow of urine.
The internal urethral sphincter controls involuntary urine flow from the bladder to the urethra, while the external urethral sphincter controls voluntary urine flow. The internal sphincter is made of smooth muscle and is under involuntary or autonomic control. The external sphincter is made of skeletal muscle and is under voluntary control.
Damage to the urethral sphincters can lead to urinary incontinence. Weak pelvic floor muscles, intrinsic sphincter damage, or damage to the surrounding nerves and tissue can make the urethral sphincter incompetent, resulting in stress urinary incontinence.
You can train your bladder to hold urine better by following a timetable to store and release urine. You can also learn to decrease the urge to urinate through Kegel exercises, which strengthen the muscles near the urethra.
