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The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder. It is the main muscle component of the urinary bladder wall and is responsible for the bladder's ability to contract and relax. The detrusor muscle remains relaxed to allow the bladder to store urine and contracts during urination to release urine. The muscle is controlled by the autonomic nervous system, with parasympathetic inputs stimulating contraction and sympathetic inputs inhibiting it to allow the bladder to fill with urine.
| Characteristics | Values |
|---|---|
| Definition | Smooth muscle found in the wall of the bladder |
| Alternative Names | Detrusor urinae muscle, muscularis propria of the urinary bladder, detrusor |
| Function | Contracts during urination to release urine; remains relaxed to allow the bladder to store urine |
| Composition | Smooth muscle cells (SMC) organised in three sheets; two longitudinal sheets surrounding a middle, circular sheet |
| Appearance | Interlacing network of multi-directional smooth muscle fibres that produce a trabeculated appearance |
| Control | Controlled by the autonomic nervous system; parasympathetic inputs stimulate contraction, sympathetic inputs stimulate relaxation |
| Ageing | In older adults over 60, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention |
| Clinical Significance | Functional changes in the detrusor muscle are associated with clinically important conditions such as lower urinary tract symptoms (LUTS) and bladder outlet obstruction |
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What You'll Learn
- The detrusor muscle is a component of the urinary bladder wall
- It contracts to release urine and relaxes to store urine
- The detrusor muscle is made of smooth muscle cells
- The muscle fibres are arranged in a swirl/whorl pattern
- Functional changes in the detrusor muscle can lead to lower urinary tract symptoms
The detrusor muscle is a component of the urinary bladder wall
The detrusor muscle, also known as the detrusor urinae muscle, is a component of the urinary bladder wall. It is a smooth muscle that facilitates the contraction of the bladder wall during micturition or urination. The detrusor muscle is made up of smooth muscle cells (SMC) that are organised in three sheets or layers—two longitudinal sheets surrounding a circular middle sheet. These sheets form an interlacing network of multidirectional muscle fibres that produce a trabeculated appearance. The detrusor muscle is innervated by the autonomic nervous system, with parasympathetic inputs stimulating its contraction and sympathetic inputs keeping it relaxed to allow the bladder to fill with urine.
The detrusor muscle plays a crucial role in bladder function, which has two main modes: urine storage and urination. During the storage phase, the detrusor muscle remains relaxed, allowing the bladder to expand and fill with urine. This relaxation is facilitated by sympathetic branches from the inferior hypogastric plexus. The bladder walls stretch as the bladder fills, and this stretch is sensed by bladder afferent neurons, providing a sense of bladder fullness.
During the urination phase, the detrusor muscle contracts, causing the bladder to expel urine. This contraction is stimulated by parasympathetic inputs, specifically the pelvic splanchnic nerves acting on postganglionic M3 receptors. At the same time, the internal and external urethral sphincters relax, allowing the urine to be released. The coordination of these processes ensures effective urination.
Disturbances in the function of the detrusor muscle can lead to various urinary issues. For example, involuntary contractions of the detrusor muscle during the storage phase can result in overactive bladder syndrome, characterised by symptoms such as urgency, frequency, and urge incontinence. In older adults, the detrusor muscle may cause problems in completely emptying the bladder, leading to uncomfortable urinary retention. Functional changes in the detrusor muscle are also associated with conditions such as lower urinary tract symptoms (LUTS) and bladder outlet obstruction.
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It contracts to release urine and relaxes to store urine
The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder. It is the main muscle component of the urinary bladder wall and is responsible for the contraction of the bladder wall during micturition or urination. The detrusor muscle contracts to release urine and relaxes to store urine in the bladder.
The detrusor muscle is composed of smooth muscle cells (SMC) organized in three sheets, with two longitudinal smooth muscle sheets surrounding a middle circular smooth muscle sheet. The muscle fibres are arranged in a swirl or whorl pattern, allowing them to act in unison to provide a mass contraction of the bladder. The detrusor muscle is innervated by the autonomic nervous system, with parasympathetic inputs stimulating its contraction and sympathetic inputs inhibiting this process to allow the bladder to relax and fill with urine.
During urination, parasympathetic pelvic splanchnic nerves act on postganglionic M3 receptors to cause contraction of the detrusor muscle. This contraction leads to the release of urine from the bladder. At other times, the muscle is kept relaxed through sympathetic branches from the inferior hypogastric plexus, allowing the bladder to fill with urine for storage. The bladder's ability to contract and relax determines its function during filling and micturition, and disturbances in these processes can lead to lower urinary tract symptoms (LUTS) such as urgency, frequency, and urge incontinence.
The detrusor muscle plays a crucial role in the two main functions of the bladder: storing and emptying urine. The bladder relaxes during the filling phase to store urine at low pressure. When it is time to release urine, the detrusor muscle contracts, and the urethra relaxes to allow for urine excretion. This coordination between the contraction of the bladder and the relaxation of the urethra is essential for effective urination.
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The detrusor muscle is made of smooth muscle cells
The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder. It is composed of smooth muscle cells (SMCs) that are organised into three layers: two longitudinal sheets on the outside and inside, with a circular sheet in the middle. This arrangement allows the detrusor muscle to contract during urination to release urine and relax at other times to allow the bladder to fill with urine.
The detrusor muscle is an important component of the urinary system, working in conjunction with the urethral sphincter muscles to control the flow of urine. During urination, parasympathetic pelvic splanchnic nerves cause the detrusor muscle to contract, while at other times, sympathetic branches from the inferior hypogastric plexus keep the muscle relaxed. This relaxation allows the bladder to store urine until it is ready to be released.
The detrusor muscle is an interlacing network of multi-directional smooth muscle fibres, giving it a trabeculated appearance. These fibres arise from the posterior surface of the body of the pubis in both sexes, with fibres in males originating from the prostate and those in females from the front of the vagina. At the sides of the bladder, the fibres intersect each other and are arranged obliquely.
Research into the detrusor muscle has provided insights into its complex physiology, including the identification of two distinct types of muscle activity: phasic activity and global contractions. Phasic activity involves localised "stretches" in small regions of the muscle associated with increases in bladder pressure. On the other hand, global contractions involve most of the bladder smooth muscle and are triggered by high-dose muscarinics and high-frequency nerve stimulation.
Understanding the physiology and function of the detrusor muscle is crucial for managing urinary disorders and developing effective treatments. For example, in older adults over 60, the detrusor muscle may cause issues with voiding the bladder, leading to uncomfortable urinary retention. By studying the detrusor muscle, researchers can develop treatments such as pharmacological agonists that target specific receptors to treat overactive bladder symptoms.
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The muscle fibres are arranged in a swirl/whorl pattern
The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder. It is responsible for the contraction of the bladder wall during micturition (urination). The detrusor muscle is made up of three layers of muscles: two longitudinal smooth muscle sheets surrounding a middle circular smooth muscle sheet. These sheets are composed of interlacing muscle fibres that run in multiple directions, forming a swirl or whorl pattern.
The muscle fibres of the detrusor are organised in this swirl/whorl pattern to enable them to work together to provide a full contraction of the bladder. This contraction is essential for expelling urine from the bladder during urination. The swirl pattern allows for a unified contraction, ensuring that the bladder can effectively empty its contents.
The detrusor muscle is innervated by the autonomic nervous system, which controls its contraction and relaxation. During urination, parasympathetic nerves stimulate the contraction of the detrusor muscle, while sympathetic nerves inhibit it, allowing the bladder to fill with urine. This coordination between contraction and relaxation of the detrusor muscle and the urethral sphincters ensures efficient urination and urine storage.
The detrusor muscle plays a crucial role in bladder function, and its ability to contract and relax determines the bladder's ability to fill and empty. When the bladder is filling, the detrusor muscle remains relaxed, allowing the bladder to expand and store urine. During urination, the detrusor muscle contracts, forcing urine out of the bladder. This coordination between the detrusor muscle and the urethral sphincters ensures effective urination and urine storage.
In older adults over 60 years of age, the detrusor muscle may cause issues in completely emptying the bladder, resulting in uncomfortable urinary retention. This can lead to symptoms such as hesitancy, weak stream, and a feeling of incomplete bladder emptying. Research into the detrusor muscle's physiology has enhanced our understanding of its coordinated contractions and relaxations, aiding in the development of treatments for bladder control issues.
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Functional changes in the detrusor muscle can lead to lower urinary tract symptoms
The detrusor muscle, also known as the detrusor urinae muscle or muscularis propria of the urinary bladder, is a smooth muscle found in the wall of the bladder. It is responsible for the bladder's ability to contract and relax, allowing for the storage and release of urine. The detrusor muscle is composed of three layers of muscle fibres that work together to enable bladder function during filling and micturition.
Additionally, detrusor pathology can lead to urinary retention, incontinence, or a combination of both. Untreated abnormalities in the detrusor muscle can cause deterioration of the upper urinary tracts. Pelvic floor muscle training and bladder training are often recommended as conservative treatment options for overactive bladder. If these initial therapies are ineffective, pharmacological and surgical treatments are also available.
In older adults over 60 years of age, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention. This can lead to symptoms such as hesitancy, weak stream, and a feeling of incomplete bladder emptying. Furthermore, cancer invading the detrusor muscle is considered a T2 lesion, which has an increased risk of nodal and distant metastasis. In such cases, the standard treatment involves the removal of the urinary bladder (radical cystectomy) and the diversion of urine.
In summary, functional changes in the detrusor muscle can lead to a range of lower urinary tract symptoms, including overactive bladder syndrome, urinary retention, and incontinence. These issues can have a significant impact on an individual's quality of life and may require conservative, pharmacological, or surgical interventions. Understanding the role of the detrusor muscle in bladder function is crucial for managing and treating these symptoms effectively.
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Frequently asked questions
The detrusor muscle, also known as the detrusor urinae muscle, is the smooth muscle component of the urinary bladder.
The detrusor muscle is the main muscle component of the bladder wall. It contracts during urination to release urine and remains relaxed to allow the bladder to store urine.
The detrusor muscle is made of smooth muscle cells (SMC) organised in three sheets. Two longitudinal sheets surround a middle, circular sheet.
The detrusor muscle is controlled by the autonomic nervous system. Parasympathetic inputs stimulate the contraction of the detrusor muscle during urination, while sympathetic inputs keep the muscle relaxed to allow the bladder to fill with urine.
Disturbances in the detrusor muscle can lead to lower urinary tract symptoms (LUTS) such as urgency, frequency, and urge incontinence, which are components of overactive bladder syndrome. In older adults, the detrusor muscle may cause issues in emptying the bladder, resulting in uncomfortable urinary retention.
