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The urinary bladder is a hollow organ that holds urine. It is composed of four distinct layers, one of which is the detrusor muscle. This is a thick layer of smooth muscle that makes up the wall of the bladder. The detrusor muscle contracts to expel urine from the bladder and relaxes to allow the storage of urine. It is innervated by the autonomic nervous system, which stimulates contraction and relaxation. The bladder neck is a narrow group of muscles that connect to the urethra.
| Characteristics | Values |
|---|---|
| Primary function | Contract during urination to push urine out of the bladder and into the urethra |
| Secondary function | Relax to allow the storage of urine in the urinary bladder |
| Location | Within the walls of the bladder |
| Composition | Three layers of typical smooth muscle cells, with the inner and outer layers oriented longitudinally and the middle one circularly |
| Control | Autonomic control, with input from the sympathetic and parasympathetic nervous systems |
| Relaxation | Caused by the hypogastric nerve, promoting urine retention |
| Contraction | Caused by the pelvic nerve, stimulating micturition |
| Abnormalities | Can lead to urinary retention, incontinence, or a combination of both |
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What You'll Learn
- The detrusor muscle is a smooth muscle layer that contracts to expel urine
- The bladder wall is made up of detrusor muscle fibres oriented in multiple directions
- The bladder neck is a narrow group of muscles that connect to the urethra
- The autonomic nervous system controls the detrusor muscle
- The parasympathetic nervous system stimulates the bladder to contract and empty
The detrusor muscle is a smooth muscle layer that contracts to expel urine
The urinary bladder is a hollow, spherical organ that holds urine. It is located in the abdomen and can hold about two cups of urine. The bladder is made up of four distinct layers, one of which is the detrusor muscle. This muscle is located within the walls of the bladder and is composed of smooth muscle fibres that are longitudinal and circular.
The detrusor muscle is made up of three layers of smooth muscle cells. The inner and outer layers are oriented longitudinally, and the middle layer is circular. This orientation is important as it determines the shape and pressure of the bladder. During the storage phase, the muscle cells are relaxed and elongated, while during the voiding phase, they contract and shorten in a synchronised way to expel urine.
The detrusor muscle is thicker in males than in females as greater pressure is needed to overcome the resistance posed by the longer male urethra. Abnormalities of the detrusor muscle can lead to urinary retention, incontinence, or deterioration of the upper urinary tracts.
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The bladder wall is made up of detrusor muscle fibres oriented in multiple directions
The urinary bladder is a hollow, spherical organ that holds urine. It is part of the urinary system and is located in the abdomen. The bladder is composed of four distinct layers, with the muscularis propria being the thick muscle layer on the outside of the bladder. This layer is also known as the detrusor muscle, which is composed of smooth muscle fibres oriented in multiple directions.
The detrusor muscle is located within the walls of the bladder and is responsible for the contraction of the bladder during urination. It is composed of three layers of smooth muscle cells, with the inner and outer layers oriented longitudinally and the middle layer oriented circularly. This orientation is important as it determines the bladder's shape and intraluminal pressure. The detrusor muscle contracts to expel urine from the bladder and relaxes to allow the storage of urine.
The process of urination involves the contraction of the detrusor muscle and the relaxation of the urethral sphincter, which allows urine to flow out of the body. The detrusor muscle is under autonomic control, receiving input from both the sympathetic and parasympathetic nervous systems. When urine fills the bladder, stretch receptors in the bladder are stimulated, leading to the contraction of the detrusor muscle. At the same time, the parasympathetic fibres inhibit the internal urethral sphincter, causing relaxation and allowing the bladder to empty.
The orientation of the detrusor muscle fibres in multiple directions provides the bladder with the ability to stretch in response to the presence of urine. This is an important function as it allows the bladder to expand and accommodate varying amounts of urine. The detrusor muscle also plays a role in maintaining urinary control and abnormalities in this muscle can lead to urinary retention, incontinence, or a combination of both.
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The bladder neck is a narrow group of muscles that connect to the urethra
The bladder is a hollow, muscular organ that holds urine. It is part of the urinary system and is located in the abdomen. The bladder neck is situated along the base of the bladder. It is a narrow group of muscles that connect to the urethra.
The bladder neck is a critical component of the urinary system, facilitating the passage of urine from the bladder to the urethra. This narrow muscular band provides structural support and aids in controlling the flow of urine. The bladder neck is composed of smooth muscle fibres that are arranged in a specific orientation. These fibres contribute to the overall function of the bladder and ensure the efficient elimination of urine.
The bladder neck is part of the detrusor muscle, which makes up the walls of the bladder. This muscle is composed of smooth muscle fibres oriented in multiple directions, giving the bladder its ability to stretch and contract. The detrusor muscle works in conjunction with the urethral sphincter to enable urination. When the bladder fills with urine, the detrusor muscle contracts, while the urethral sphincter relaxes, allowing urine to flow out of the body.
In addition to its role in urination, the detrusor muscle also helps to maintain urinary control. Abnormalities or pathologies of the detrusor muscle can lead to urinary retention, incontinence, or a combination of both. Proper functioning of the detrusor muscle is essential for the overall health of the urinary system. The muscle is under the control of the autonomic system, receiving input from both the sympathetic and parasympathetic nervous systems. This complex neurological control allows for the coordination of urination and the maintenance of bladder function.
The bladder neck, as part of the detrusor muscle, plays a vital role in maintaining urinary health and ensuring the smooth passage of urine. Its connection to the urethra is crucial for controlling urine flow and preventing leakage. The interplay between the bladder neck muscles and the urethral sphincter contributes to the overall efficiency of the urinary system.
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The autonomic nervous system controls the detrusor muscle
The bladder is a hollow, spherical organ in the abdomen that stores urine. It is part of the urinary system and is connected to the urethra. The bladder is composed of three main layers: the urothelium (inner lining), the lamina propria (a thin layer of loose connective tissue), and the muscularis propria (the thick muscle layer on the outside). The muscularis propria layer is made up of smooth muscle fibres that tighten and relax automatically to allow the bladder to expand and contract.
The detrusor muscle is a specialised smooth muscle that forms the walls of the bladder. Its primary function is to contract during urination to push urine out of the bladder and into the urethra. The detrusor muscle relaxes to allow the bladder to store urine. The contraction of the detrusor muscle and relaxation of the urethral sphincter lead to urination. The detrusor muscle is composed of smooth muscle fibres oriented in multiple directions, providing the bladder with the ability to stretch in response to the presence of urine.
The coordination of the bladder and urethra is modulated by the central nervous system (the brain, brainstem, and spinal cord). During infancy, as the brain matures, it gradually gains control of the bladder and urinary sphincters to inhibit involuntary voiding. This control is achieved through the sacral reflex centre and the PMC, which is further modulated by higher brain centres that process emotion and social context. The brain is considered the master control of the entire urinary system.
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The parasympathetic nervous system stimulates the bladder to contract and empty
The bladder is a hollow, spherical-shaped organ that holds urine. It is derived from the upper segment of the urogenital sinus in the fetus. The bladder is part of the urinary system and is located in the abdomen. The bladder is pink or dark pink and is about 2 inches when empty but can stretch to 6 inches when full. It consists of three main layers: the urothelium, the lamina propria (submucosa), and the muscularis propria. The muscularis propria is the thick muscle layer on the outside of the bladder. It consists of three layers of smooth muscle.
The parasympathetic nervous system is a network of nerves that relaxes the body after periods of stress or danger. It also helps run life-sustaining processes, like digestion, during times when one feels safe and relaxed. The parasympathetic nervous system is part of the autonomic nervous system. It is responsible for many functions that occur without conscious thought, such as control of heart rate, blood pressure, digestion, urination, and sweating. While the sympathetic nervous system controls the body's "fight or flight" response, the parasympathetic nervous system helps control the body's response during times of rest.
The bladder receives input from both the autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system. The sympathetic nervous system causes relaxation of the detrusor muscle, promoting urine retention. The parasympathetic nervous system, on the other hand, increases signals from the pelvic nerve, leading to contraction of the detrusor muscle and stimulation of micturition. The somatic nervous system, through the pudendal nerve, innervates the external urethral sphincter, providing voluntary control over micturition.
Problems with the parasympathetic nervous system can cause incontinence when there is damage to the nerves that control the bladder and bowels. Paraplegic patients, or those who have lost descending control of the sacral spinal cord, may experience incomplete bladder emptying due to the loss of voluntary control over micturition. This can lead to chronic urinary tract infections from retained urine, requiring the use of an indwelling catheter to ensure adequate drainage.
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Frequently asked questions
The detrusor muscle is a smooth muscle layer that makes up the walls of the bladder. It is composed of interlacing randomly oriented muscle fibres.
The detrusor muscle contracts during urination to push urine out of the bladder and into the urethra. When the bladder is being filled, the detrusor muscle relaxes to allow the bladder to store urine.
Abnormalities in the detrusor muscle can lead to urinary retention, incontinence, or a combination of both. In older adults, the detrusor muscle may cause issues in voiding the bladder, resulting in uncomfortable urinary retention.
