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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 responsible for the contraction of the bladder wall during urination, allowing urine to be released. The detrusor muscle is composed of interlacing muscle fibres that run in multiple directions, giving it a trabeculated appearance. It is the main muscle component of the bladder and plays a crucial role in bladder function, including the sensation of a full bladder and the contraction that leads to urinary expulsion.
| Characteristics | Values |
|---|---|
| Name | Detrusor muscle, detrusor urinae muscle, muscularis propria of the urinary bladder |
| Type | Smooth muscle |
| Location | Wall of the bladder |
| Function | Contracts during urination to release urine, remains relaxed to allow the bladder to store urine |
| Structure | Interlacing network of multi-directional smooth muscle fibres, forming a swirl/whorl type pattern |
| Layers | Inner (longitudinal), middle (circumferential), outer (longitudinal) |
| Sex Differences | More developed in males due to the need to generate greater pressure to overcome resistance from the longer male urethra |
| Cellular Composition | Typical smooth muscle cells, long and spindle-shaped with a central nucleus, packed with myofilaments, dense bands, membrane vesicles, and scattered dense bodies in the cytoplasm |
| Cellular Size | Several hundred microns long, widest diameter of 5-6 μm |
| Bundles | Composed of sub-bundles of varying sizes surrounded by collagen-rich connective tissue |
| Receptors | Stretch receptors responsible for the sensation of a full bladder |
| Pathological Conditions | Lower urinary tract symptoms (LUTS), bladder outlet obstruction, detrusor hypertrophy, detrusor overactivity, OAB (patchy denervation of muscle bundles) |
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What You'll Learn
The detrusor muscle is the main muscle component of the urinary bladder wall
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 composed of interlacing muscle fibres that run in multiple directions, giving it a trabeculated appearance. The detrusor muscle is responsible for the contraction of the bladder wall during micturition or urination.
The individual smooth muscle cells in the detrusor are typical smooth muscle cells similar to those found in other muscular organs. They are long, spindle-shaped cells with a central nucleus. These cells are several hundred microns long when fully relaxed, with a width of 5-6 μm. The cytoplasm contains myofilaments, and the membranes have regularly spaced dense bands with membrane vesicles between them. Additionally, there are scattered dense bodies in the cytoplasm, along with mitochondria and sparse elements of the sarcoplasmic reticulum.
In the human detrusor, bundles of muscle cells of varying sizes are surrounded by connective tissue rich in collagen. These bundles can be a few millimetres in diameter and consist of smaller sub-bundles. The cells within these bundles may have long dendritic processes parallel to the smooth muscle fibres, containing vimentin and non-muscle myosin. While the functional importance of these cells is not yet fully understood, they may exist in groups of small functional units called fascicles.
The detrusor muscle works in conjunction with the urethral sphincter muscles, which control the flow of urine. During urination, the detrusor muscle contracts to expel urine from the bladder into the urethra. The fibres of the detrusor muscle arise from the posterior surface of the pubis and attach to the prostate in males or the front of the vagina in females. Near the internal urethral meatus, the fibres form three specific layers (inner longitudinal, middle circumferential, and outer longitudinal), creating the proximal bladder neck sphincter.
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It contracts to release urine and remains relaxed 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 an interlacing network of multidirectional smooth muscle fibres that give the muscle a trabeculated appearance. The detrusor muscle is responsible for the contraction of the bladder wall during micturition (urination).
The detrusor muscle is the main muscle component of the urinary bladder wall. Its ability to contract and relax determines the bladder's function during filling and micturition. During urination, the detrusor muscle contracts to release urine, and between urinations, it remains relaxed to allow the bladder to store urine. This process is regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signalling pathways.
The detrusor muscle fibres arise from the posterior surface of the body of the pubis in both sexes (musculi pubovesicales). In males, the fibres also arise from the adjacent part of the prostate. These fibres pass in a longitudinal manner up the inferior surface of the bladder, over its apex, and then descend along its fundus to become attached to the prostate or the front of the vagina in females. At the sides of the bladder, the fibres intersect each other in an oblique arrangement.
Near the bladder neck, the detrusor muscle is continuous with the internal urethral sphincter. Here, the detrusor muscle fibres orient themselves into three specific layers: inner longitudinal, middle circumferential, and outer longitudinal. These layers form the proximal bladder neck sphincter. The detrusor muscle in males is generally better developed than in females as greater pressure is needed to overcome the resistance posed by the longer male urethra.
The individual smooth muscle cells in the detrusor are similar to those in other muscular organs. They are long, spindle-shaped cells with a central nucleus. When fully relaxed, these cells can be several hundred microns long, with a width of 5-6 μm. The cytoplasm contains myofilaments, and the membranes have regularly spaced dense bands with membrane vesicles (caveoli) between them.
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It is composed of interlacing muscle fibres
The detrusor muscle, also known as the detrusor urinae muscle or muscularis propria of the urinary bladder, is composed of interlacing muscle fibres. It is a smooth muscle found in the wall of the bladder. The detrusor muscle's main function is to contract during urination to release urine. When the bladder is relaxed, the detrusor muscle remains relaxed to allow the bladder to store urine.
The detrusor muscle is an interlacing network of multi-directional smooth muscle fibres that produce a trabeculated appearance on gross inspection. The muscle fibres run randomly in all directions, forming a swirl or whorl pattern to act in unison and provide mass contraction of the bladder. Only near the internal urethral meatus do the fibres orient themselves into three specific layers: inner longitudinal, middle circumferential, and outer longitudinal. These layers form the proximal bladder neck sphincter.
The detrusor muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and urination. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signalling pathways.
The individual smooth muscle cells in the detrusor are typical smooth muscle cells, similar to those found in other muscular organs. They are long, spindle-shaped cells with a central nucleus. When fully relaxed, these cells can be several hundred microns long, with a width of 5-6 μm. The cytoplasm contains normal myofilaments, and the membranes have regularly spaced dense bands with membrane vesicles (caveoli) between them. There are also scattered dense bodies in the cytoplasm, along with mitochondria and sparse elements of the sarcoplasmic reticulum.
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Detrusor strength is the best measure of detrusor muscle function
The detrusor muscle is a smooth muscle found in the wall of the bladder. It is composed of interlacing muscle fibres that run in multiple directions, giving the bladder the ability to stretch in response to the presence of urine. The detrusor muscle is responsible for contracting during urination to expel urine from the bladder into the urethra. It remains relaxed when the bladder is storing urine. The detrusor muscle is innervated by the autonomic nervous system and its contraction is stimulated by the parasympathetic nervous system through the activation of M3 receptors.
The functional ability of the detrusor muscle to contract appropriately can be altered by various factors such as aging, atrophy, trauma, or decreased muscular innervation. These factors can lead to conditions such as detrusor overactivity, which is commonly associated with urgency incontinence, especially in older women.
Detrusor strength, which refers to the force of contraction of the detrusor muscle, is considered the best measure of detrusor muscle function. This is because the primary function of the detrusor muscle is to contract and expel urine from the bladder. By assessing the strength of the detrusor muscle, we can gain insights into its overall functionality and identify any potential issues or abnormalities.
While contraction speed and duration are also important aspects of detrusor muscle function, they are often overlooked. A comprehensive assessment of detrusor muscle function should consider not only the strength but also the speed and duration of contractions. This multi-faceted approach helps to fully understand the muscle's performance and identify any deviations from normal function.
In conclusion, detrusor strength is indeed the best measure of detrusor muscle function as it directly evaluates the muscle's ability to contract and expel urine, which is its primary physiological role. However, it is important to also consider other factors such as contraction speed and duration to obtain a complete understanding of detrusor muscle function and identify any potential issues related to urinary health.
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It is also known as detrusor urinae muscle
The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder. It is also referred to as the muscularis propria of the urinary bladder. This muscle is responsible for the contraction of the bladder during urination, allowing urine to be released. When not in use, the detrusor muscle remains relaxed, allowing the bladder to store urine.
The detrusor muscle is composed of interlacing muscle fibres that run in multiple directions, forming a network that gives the bladder a trabeculated appearance. This muscle is innervated by the autonomic nervous system, which controls its contraction and relaxation. During urination, parasympathetic pelvic splanchnic nerves cause the detrusor muscle to contract, while at other times, sympathetic branches keep it relaxed to allow the bladder to fill with urine.
In addition to its role in urination, the detrusor muscle is also involved in maintaining urinary health. Abnormalities or pathologies of the detrusor muscle can lead to urinary retention, incontinence, or a combination of both. If left untreated, these issues can result in further complications, such as deterioration of the upper urinary tracts.
The detrusor muscle is also related to the urethral sphincter muscles, which envelop the urethra and control the flow of urine through contraction. In males, the detrusor muscle fibres arise from the prostate, while in females, they attach to the front of the vagina. These fibres pass longitudinally along the bladder and intersect each other at the sides, forming a swirl or whorl pattern that enables mass contraction.
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Frequently asked questions
The detrusor muscle, also known as the detrusor urinae muscle, is a smooth muscle found in the wall of the bladder.
The detrusor muscle remains relaxed to allow the bladder to store urine and contracts during urination to release urine.
The detrusor muscle is an interlacing network of multi-directional smooth muscle fibres. The fibres are arranged in three specific layers near the internal urethral meatus: inner longitudinal, middle circumferential, and outer longitudinal.
The detrusor muscle in males is better developed than in females as greater pressure is needed to overcome the resistance posed by the longer male urethra.
The detrusor muscle's stretch receptors are responsible for the sensation of a full bladder, and its contraction from efferent parasympathetic impulses is responsible for emptying the bladder.
