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The urinary tract is the body's drainage system for removing urine. It includes two kidneys, two ureters, a bladder, and a urethra. The urinary tract includes two sets of muscles that work together as a sphincter, closing off the urethra to keep urine in the bladder. The detrusor muscle surrounds the bladder and allows the bladder to contract to excrete urine or relax to hold urine. The pelvic floor muscles also support the bladder, bowel, and uterus. They give you the ability to control the release of urine. When you contract the pelvic floor muscles, they lift the internal organs of the pelvis and tighten the openings of the vagina, anus, and urethra.
| Characteristics | Values |
|---|---|
| Muscle that cuts off urine | Pelvic floor muscles |
| Location | Surrounds the urethra, bladder, bowel, and vagina |
| Function | Controls the release of urine, faeces, and flatus |
| Control | Under conscious control |
| Strengthening exercises | Kegel exercises |
| Weakening factors | Age, pregnancy, heavy lifting, high-impact exercises, ongoing cough, etc. |
| Related medical conditions | Urinary retention, incontinence, urinary tract infection, pelvic organ prolapse |
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What You'll Learn
- The detrusor muscle surrounds the bladder and contracts to push urine out
- The internal urethral sphincter relaxes to allow urine to pass out of the bladder
- The external urethral sphincter is voluntary and must be relaxed for urination
- Pelvic floor muscles control the release of urine and can be strengthened by Kegel exercises
- The urinary sphincter is a muscle that blocks urine flow when contracted
The detrusor muscle surrounds the bladder and contracts to push urine out
The detrusor muscle is a smooth muscle that surrounds the bladder and is composed of smooth muscle fibres that are longitudinal and circular. It is located within the bladder walls and is responsible for the contraction of the bladder during urination. The detrusor muscle contracts to push urine out of the bladder and into the urethra.
The detrusor muscle is under autonomic control and is influenced by the parasympathetic nervous system, which stimulates the bladder through pelvic nerve fibres. When the bladder fills with urine, stretch receptors in the bladder wall, specifically the M3 receptors, become activated, leading to the contraction of the detrusor muscle. This contraction is essential for initiating the process of urination.
At the same time, the parasympathetic fibres inhibit the internal urethral sphincter, causing it to relax. This relaxation of the internal urethral sphincter, located at the neck of the bladder, allows urine to pass out of the bladder. The internal sphincter is involuntary and remains closed until the brain signals the need to urinate.
The detrusor muscle works in conjunction with the internal and external urethral sphincters to control the flow of urine. While the detrusor muscle contracts to push urine out, the internal sphincter relaxes to open the passage. The external urethral sphincter, which surrounds the urethra outside the bladder, is under voluntary control. For urination to occur, this external sphincter must also relax, allowing urine to flow through the urethra and out of the body.
The coordination between the detrusor muscle and the urethral sphincters is crucial for maintaining urinary control and ensuring the smooth passage of urine during the process of urination.
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The internal urethral sphincter relaxes to allow urine to pass out of the bladder
The urinary tract is the body's drainage system for removing urine. It includes the kidneys, ureters, bladder, and urethra. The bladder is a muscular organ that stores urine before it is released from the body during urination.
The process of urination involves the coordination of various muscles in the urinary tract. The bladder is surrounded by a smooth muscle called the detrusor muscle, which contracts to push urine out of the bladder during urination. At the same time, the internal urethral sphincter, located at the inferior end of the bladder, relaxes to allow urine to pass out of the bladder and into the urethra.
The internal urethral sphincter is an involuntary muscle that surrounds the opening of the bladder to the urethra. It normally remains closed, preventing urine from leaking out. When the bladder fills with urine, stretch receptors in the bladder wall are activated, triggering the micturition reflex, or the urge to urinate. This causes the detrusor muscle to contract and the internal urethral sphincter to relax, allowing urine to pass out of the bladder.
The external urethral sphincter, which surrounds the urethra outside the bladder, is a voluntary muscle that also plays a role in controlling urination. It must be relaxed for urination to occur. During urination, the brain signals the internal and external sphincters to relax, followed by signalling the detrusor muscle to contract, allowing urine to be released from the bladder and passed out of the body through the urethra.
The pelvic floor muscles also contribute to urinary control by supporting the bladder and surrounding the urethra. These muscles can be contracted to prevent the release of urine and relaxed to allow urine to pass. Pelvic floor exercises, such as Kegel exercises, can help strengthen these muscles and improve urinary control.
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The external urethral sphincter is voluntary and must be relaxed for urination
The urinary tract includes two sets of muscles that work together as a sphincter, closing off the urethra to keep urine in the bladder. The internal sphincter muscles of the bladder neck and urethra remain closed until the brain sends signals to urinate. The external sphincter muscles, or the external urethral sphincter, are under voluntary control and surround the internal sphincter to provide extra pressure to keep the urethra closed.
The external urethral sphincter is a voluntary muscle that surrounds the urethra outside the bladder. It must be relaxed for urination to occur. This muscle is under conscious control, which means that it can be contracted or squeezed to keep urine from leaking out. To urinate, the brain signals the external urethral sphincter to relax, and then it signals the muscular bladder wall to contract, allowing urine to pass through the urethra and out of the body.
The external urethral sphincter works in conjunction with the internal urethral sphincter, which is involuntary. The internal sphincter surrounds the opening of the bladder to the urethra and relaxes 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. This sends signals through the nervous system, creating the "urge" to urinate.
The pelvic floor muscles also play a crucial role in controlling the release of urine. These muscles support the bladder, bowel, and uterus in women, and the bladder and bowel in men. By contracting the pelvic floor muscles, the openings of the vagina, anus, and urethra are tightened, preventing the release of urine. Relaxing the pelvic floor muscles allows for the passage of urine. Maintaining strong pelvic floor muscles through exercises like Kegels can help prevent urinary incontinence and promote healthy bladder function.
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Pelvic floor muscles control the release of urine and can be strengthened by Kegel exercises
The pelvic floor muscles are essential for maintaining bladder and bowel control. They support the bladder, bowel, and uterus (womb) in women, and the bladder and bowel in men. These muscles wrap around the urethra, anus, and vagina, helping to keep them closed. By contracting and relaxing, the pelvic floor muscles allow the passage of urine, faeces, and flatus.
The pelvic floor muscles can be consciously squeezed to prevent urine leakage. They can also be exercised through Kegel exercises, which involve tightening and releasing the muscles to strengthen them. Kegel exercises were developed in the 1940s by Dr Arnold H. Kegel as a non-surgical way to prevent urinary leakage. Both men and women can benefit from these exercises, which can improve sexual health and orgasms.
To perform Kegel exercises, it is important to first identify the correct muscles. This can be done by stopping the flow of urine while sitting on the toilet or by pretending to prevent the passing of gas. Once the correct muscles are identified, they can be tightened and released in short or long contractions. Aim for at least 30 to 40 Kegel exercises per day, spreading them throughout the day.
It is important to note that Kegel exercises may not be suitable for everyone. While they can help prevent urine leakage, doing too many Kegels can cause the muscles to become too tense or tight. Additionally, certain conditions, such as obesity, surgery in the pelvic area, and ageing, can weaken the pelvic floor muscles, requiring extra care when performing these exercises.
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The urinary sphincter is a muscle that blocks urine flow when contracted
The urinary sphincter is a muscle that controls the flow of urine out of the bladder. When the urinary sphincter is contracted, it blocks the opening of the bladder, preventing urine from leaking out. Typically, the urinary sphincter remains closed until an individual chooses to relax it to pass urine. When the urinary sphincter is relaxed, urine exits the bladder and flows out of the body through the urethra.
The urinary tract includes two sets of muscles that work together as a sphincter, sealing the urethra to retain urine in the bladder. The internal sphincter muscles of the bladder neck and urethra remain closed until the brain sends signals to urinate. The external sphincter muscles surround the internal sphincter and provide additional pressure to keep the urethra closed. Individuals can consciously squeeze the external sphincter and the pelvic floor muscles to prevent urine from leaking.
The pelvic floor muscles are essential for controlling the release of urine. They lift the internal organs of the pelvis and tighten the openings of the vagina, anus, and urethra. Relaxing the pelvic floor muscles allows urine to pass. These muscles are also crucial for sexual function in both men and women. In men, they are essential for erectile function and ejaculation, while in women, they contribute to sexual sensation and arousal.
The detrusor muscle, which surrounds the bladder, also plays a role in urine retention and release. This smooth muscle contracts during urination, pushing urine out of the bladder and into the urethra. When the bladder is empty, the detrusor muscle relaxes to allow the storage of urine. The combination of detrusor contraction and urethral sphincter relaxation leads to urination.
In some cases, individuals may experience difficulty controlling their urinary sphincter, leading to urine leakage. This can occur after prostate surgery or radiation therapy. When conservative treatments fail, an artificial urinary sphincter (AUS) may be implanted surgically. The AUS functions similarly to the natural urinary sphincter, controlling the flow of urine and allowing voluntary urination.
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Frequently asked questions
The detrusor muscle surrounds the bladder and allows the bladder to contract to excrete urine or relax to hold urine. The detrusor muscle works in conjunction with the internal and external urethral sphincters to control the flow of urine. The internal sphincter muscles are involuntary and relax to allow urine to pass, while the external sphincter muscles are voluntary and must be relaxed for urination to occur.
The detrusor muscle contracts during urination to push urine out of the bladder and into the urethra. It is composed of smooth muscle fibres oriented in multiple directions, which allows the bladder to stretch in response to the presence of urine. The detrusor muscle is controlled by the autonomic nervous system.
Pelvic floor exercises, also known as Kegel exercises, can help strengthen the muscles that control urine flow. These exercises involve tightening and releasing the pelvic floor muscles to improve bladder control and prevent leakage. Maintaining a healthy lifestyle, including regular physical activity, limiting alcohol intake, reducing caffeine consumption, and avoiding smoking, can also contribute to healthy urine-holding muscles.
