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The urethra is a tube that connects the bladder to the external urethral meatus. It is surrounded by muscle layers and has two sphincters, or muscles that act as valves to control the flow of urine. The internal sphincter is an involuntary muscle, while the external sphincter is under voluntary control. These muscles work together with the bladder to expel urine from the body. The urethra is also involved in sexual reproduction, as it is the conduit for semen during orgasm. In females, the urethra is about 1.5 inches long, while in males, it is about 8 to 9 inches long.
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What You'll Learn
- The urethra has two types of sphincter muscles that control the flow of urine
- The internal sphincter is involuntary and the external sphincter is under voluntary control
- The urethra is surrounded by three muscle layers from the lumenal side
- The urethra is a fibrous and muscular tube that connects the bladder to the external urethral meatus
- Urinary incontinence can be caused by urethral sphincter incompetence due to nerve and muscle damage
The urethra has two types of sphincter muscles that control the flow of urine
The urethra is a fibrous and muscular tube that connects the urinary bladder to the external urethral meatus. The walls of the tube are thin and made up of epithelial tissue, smooth muscle cells, and connective tissue. The urethra has two types of sphincter muscles that control the flow of urine: the internal urethral sphincter and the external urethral sphincter.
The internal urethral sphincter is located at the point where the urethra leaves the bladder. It is a smooth, involuntary muscle that receives its nerve supply from the sympathetic division of the autonomic nervous system. The internal sphincter controls involuntary urine flow from the bladder to the urethra and is the primary muscle that prohibits the release of urine.
The external urethral sphincter is located in the pelvic floor in females and inferior to the prostate in males. It is a striated, skeletal muscle that allows for voluntary control over urination. The external sphincter controls voluntary urine flow from the bladder to the urethra and is the secondary muscle in control of urine flow. It is made up of three parts in females: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae. In males, the external sphincter wraps solely around the urethra.
Both sphincters work together with the bladder to get urine out of the body. When the voluntary external sphincter muscle relaxes, the involuntary internal sphincter muscle relaxes as well, allowing urine to flow out of the bladder through the urethra. When these muscles are contracted, they keep urine in the bladder. Damage to these muscles can lead to urinary incontinence.
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The internal sphincter is involuntary and the external sphincter is under voluntary control
The urethra is a tube that connects the urinary bladder to the external urethral meatus, allowing urine to pass through and leave the body. It has two different types of sphincters or muscles that act as valves to control the flow of urine: the internal urethral sphincter and the external urethral sphincter.
The internal sphincter is involuntary and is located at the opening of the bladder to the urethra. It is a smooth muscle that encircles the urethra and controls involuntary urine flow from the bladder to the urethra. The internal sphincter is formed by the involuntary smooth muscles lining the bladder neck and urethra, and it receives its nerve supply from the sympathetic division of the autonomic nervous system. It is considered the primary muscle that prohibits the release of urine.
On the other hand, the external sphincter is under voluntary control and is made of skeletal muscle. It surrounds the area of the urethra outside the bladder and is the secondary muscle in control of urine flow. The external sphincter is horseshoe-shaped in cross-section and surrounds the urethra, enveloping only the anterior and lateral sides. It controls voluntary urine flow from the bladder to the urethra. In males, the internal sphincter also prevents the flow of semen into the bladder during ejaculation.
Any damage to these muscles or surrounding nerves and tissue can lead to urinary incontinence. Weak pelvic floor muscles, intrinsic sphincter damage, or nerve damage can cause the urethral sphincter to become incompetent, resulting in involuntary urine loss. In women, childbirth, obesity, and age can weaken the pelvic floor muscles, while in men, prostate surgery and radiation therapy can damage the sphincter and cause stress incontinence.
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The urethra is surrounded by three muscle layers from the lumenal side
The urethra is a passageway located in the body's pelvic region. It is a hollow tube that allows urine to leave the body. The urethra is made up of several parts, including the membranous part, which is surrounded by three muscle layers from the lumenal side. These layers consist of longitudinal and circular muscles, which are smooth muscles, and the external urethral sphincter, which is a skeletal muscle.
The urethra has two types of sphincters or muscles that act as valves to control the flow of urine: the internal urethral sphincter and the external urethral sphincter. The internal sphincter is located at the point where the urethra exits the bladder, while the external sphincter is found in the pelvic floor. These sphincters work together with the bladder to release urine from the body. The internal sphincter is an involuntary muscle that controls the flow of urine from the bladder to the urethra, while the external sphincter is a voluntary muscle that controls the flow of urine from the urethra to the outside of the body.
In males, the internal sphincter also prevents the flow of semen into the bladder during ejaculation. The external sphincter, being a skeletal muscle, is under the control of the somatic nervous system. The smooth muscles of the urethra, including the internal sphincter, receive their nerve supply from the sympathetic division of the autonomic nervous system.
Damage to the urethral sphincters or surrounding muscles can lead to urinary incontinence. This can be caused by various factors such as childbirth in women and prostate surgery or radiation therapy in men. In women, the decrease in estrogen levels during menopause can lead to thinning of the vaginal and urethral tissue, which is a risk factor for developing intrinsic sphincter deficiency.
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The urethra is a fibrous and muscular tube that connects the bladder to the external urethral meatus
The length of the urethra varies between sexes, with the female urethra being shorter at about 1.5 inches (3 to 4 centimeters) long, while the male urethra is about 8 to 9 inches long (about 20 centimeters). The male urethra is also divided into four parts: the prostatic, membranous, penile, and preputial urethra. The female urethra has a more elaborate external sphincter muscle than the male urethra, as it is made up of three parts: the sphincter urethrae, the urethrovaginal muscle, and the compressor urethrae.
The membranous part of the urethra is surrounded by three muscle layers: longitudinal and circular muscles, which are smooth muscles, and the external urethral sphincter, which is a skeletal muscle. The external urethral sphincter is horseshoe-shaped in cross-section and surrounds the urethra, enveloping only its anterior and lateral sides. Portions of the levator and superficial transverse perineal muscles connect the external urethral sphincter to the external anal sphincter.
Damage to the urethral sphincter or surrounding muscles can lead to urinary incontinence. In women, childbirth, obesity, and age can be risk factors, especially by weakening the pelvic floor muscles. In men, prostate surgery and radiation therapy can damage the sphincter and cause stress incontinence. Urethral strictures can also occur when the urethra becomes narrower due to scarring, leading to inflammation, infections, pain during urination, and difficulty emptying the bladder.
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Urinary incontinence can be caused by urethral sphincter incompetence due to nerve and muscle damage
The urethra is a hollow tube that allows urine to leave the body. It has two types of sphincters or muscles that act as valves to control the flow of urine: the internal urethral sphincter and the external urethral sphincter. The internal sphincter is involuntary and controls urine flow from the bladder to the urethra, while the external sphincter is voluntary and controls urine flow from the bladder to the outside of the body.
Urinary incontinence is involuntary urine leakage. It can be caused by urethral sphincter incompetence, which is often due to nerve and muscle damage. This damage can be temporary or permanent and can happen due to several factors, including childbirth, surgery, radiation therapy, spinal cord injuries, and more. In women, childbirth and pregnancy can strain and weaken the muscles of the pelvic floor, causing a condition called urethral hypermobility, which can lead to stress incontinence. In men, prostate surgery and radiation therapy can damage the sphincter and cause stress incontinence.
The urethral sphincter plays a crucial role in releasing urine. When nerve and muscle damage occurs, its function is impaired, leading to urinary retention or incontinence. Specifically, damage to the pelvic floor muscles, intrinsic sphincter damage, or damage to the surrounding nerves and tissue can cause urethral sphincter incompetence. This incompetence results in the sphincter not closing fully, leading to stress urinary incontinence.
In cases of urethral sphincter incompetence, there are surgical and non-surgical treatment options available. Surgical options include procedures such as attaching the neck of the bladder to the pubic bone or ligaments, needle suspensions, and implanting an artificial internal sphincter. Non-surgical options include urethral bulking agents and adjustable continence therapy (ACT®), which involves compressing the urethra using silicone balloons to prevent urine leakage.
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Frequently asked questions
Yes, the urethra is a fibrous and muscular tube that connects the urinary bladder to the external urethral meatus.
The urethra has two types of muscles that act as valves to open or close: the internal urethral sphincter and the external urethral sphincter.
The internal urethral sphincter is a smooth, involuntary muscle that controls the involuntary flow of urine from the bladder to the urethra.
The external urethral sphincter is a skeletal muscle that controls the voluntary flow of urine from the bladder to the urethra.
Damage to the muscles in the urethra can lead to urinary incontinence, where the urethra cannot hold back urine in the bladder.
