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The urinary bladder is a temporary storage reservoir for urine located in the pelvic cavity. It is a hollow, stretchy organ in the lower abdomen that fills with urine and empties through the urethra. The bladder is composed of interwoven smooth muscle cells, interspersed with elastin and connective tissues, and lined with transitional epithelium. The bladder or detrusor muscle is composed of three layers of typical smooth muscle cells, with the inner and outer layers oriented longitudinally and the middle one circularly. This orientation allows the bladder to change shape and alter its intraluminal pressure.
| Characteristics | Values |
|---|---|
| Bladder location | Lower abdomen/pelvis |
| Bladder function | Temporary storage reservoir for urine |
| Bladder composition | Hollow, stretchy organ with three layers: Urothelium, Lamina Propria, and Muscularis Propria |
| Muscularis Propria composition | Three layers of smooth muscle cells |
| Bladder shape and pressure | Determined by the orientation of muscle cells |
| Bladder control | Autonomic nervous system, particularly the parasympathetic and sympathetic responses |
| Bladder size | Varies with the amount of urine and pressure from surrounding organs |
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What You'll Learn
The bladder is a hollow, muscular organ that stores urine
The bladder is a muscular organ that is part of the urinary system. It is a hollow, stretchy organ located in the lower abdomen or pelvic cavity, and its primary function is to store urine. The bladder receives urine excreted by the kidneys, which passes through the ureters and the ureterovesical junction into the bladder. The bladder neck, or the narrow group of muscles at the base of the bladder, connects to the urethra, which allows urine to exit the body.
The bladder wall is composed of smooth muscle fibres, known as the detrusor muscle, which is under autonomic control. The detrusor muscle contracts during urination to push urine out of the bladder and into the urethra, and relaxes to allow the storage of urine. The bladder can stretch in response to the presence of urine due to the interwoven orientation of the detrusor muscle fibres. The size and shape of the bladder vary depending on the amount of urine it contains and the pressure exerted by surrounding organs.
The process of urination is coordinated by the pontine micturition centre in the pons of the brainstem. As the bladder fills with urine, sensory nerves send signals to the central nervous system, which then controls the release of urine through stimulation of the detrusor muscle and relaxation of the internal and external urethral sphincters. The external urethral sphincter is composed of striated muscle and is under voluntary somatic control, allowing the urethra to remain closed and preventing leakage of urine during storage.
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The bladder has three layers of smooth muscle cells
The urinary bladder is a hollow, stretchy organ in the lower abdomen that holds urine until it leaves the body. The bladder is part of the urinary system and works with the kidneys to remove waste from the body. The kidneys filter the blood and remove waste products, which are then passed through the ureters to the bladder. The bladder then stores the urine until it is released from the body through the urethra.
The bladder, or detrusor muscle, is composed of three layers of smooth muscle cells. The inner and outer layers are oriented longitudinally, while the middle layer is circular. This orientation is important as it determines the shape of the bladder and its intraluminal pressure. During the storage phase, the muscle cells relax and elongate to accommodate the increasing volume of urine. In contrast, during the voiding phase, the muscle cells shorten in a synchronized manner to expel the urine from the bladder.
The bladder neck, or internal sphincter, is the narrow passage at the base of the bladder that connects to the urethra. It is composed of a coalescence of muscle fibres that form a funnel-like structure. The urethra is composed of smooth muscle, striated muscle, and a lamina propria, which includes a submucosal layer. The external urethral sphincter is composed of striated muscle and contributes to maintaining urethral pressure.
The bladder is innervated by a network of parasympathetic, sympathetic, and somatic nerve fibres. These nerves play a crucial role in controlling the filling and voiding of the bladder. Mechanoreceptors in the bladder wall detect the stretch of the muscle as the bladder fills with urine. These receptors send sensory information to the central nervous system via afferent fibres, stimulating the sympathetic response and inhibiting the parasympathetic response during the storage phase. When the bladder is full, the parasympathetic response is stimulated, leading to bladder contraction and relaxation of the internal sphincter, allowing for the release of urine.
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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 in the pelvis that stores urine until it leaves the body. The bladder neck, or bladder internal sphincter, is a narrow group of muscles located along the base of the bladder. It connects the bladder to the urethra, which is the canal through which urine passes out of the body.
The bladder neck is a funnel-like structure formed by the condensation of the bladder's muscle fibres at its base. It is not a true circular sphincter but a coalescence of muscle as the bladder drains into the urethra. The urethra extends from the bladder neck to the urethral meatus, with the female urethra being approximately 4 cm long and the male urethra beginning at the bladder neck. The bladder neck is also known as the "internal sphincter" to distinguish it from the external sphincter, which is a true sphincter composed of striated muscle that surrounds the middle third of the urethra.
The bladder neck is an important structure in maintaining urinary control and continence. It works in conjunction with the external urethral sphincter to prevent urine leakage during storage. When the bladder is empty, mechanoreceptors in the bladder wall detect the stretch of the muscle as it fills with urine. This sends sensory information to the central nervous system, which then stimulates the sympathetic response, causing the detrusor muscle and internal sphincter to relax and the external urethral sphincter to contract and remain closed. As the bladder fills, the speed of stimuli to the central nervous system increases. When the bladder is full, the parasympathetic response is stimulated, leading to contraction of the detrusor muscle and relaxation of the internal sphincter, allowing urine to pass into the urethra and out of the body.
Disorders of the bladder neck, such as bladder neck stenosis and urethral stricture, can cause bladder obstruction and incomplete bladder emptying. These disorders are often associated with prostate problems and can be treated with a bladder neck incision or urethrotomy.
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The detrusor muscle contracts during urination to push urine out
The bladder is a hollow, stretchy organ in the lower abdomen that stores urine until it leaves the body. The bladder wall is made of the detrusor muscle, which is a smooth muscle, and an overlying mucosal layer lined by uroepithelium. The detrusor muscle contracts during urination to push urine out of the bladder.
The detrusor muscle is under autonomic control. When urine fills the bladder, the parasympathetic nervous system stimulates the bladder, causing the detrusor muscle to contract and the person to urinate. The detrusor muscle is composed of three layers of smooth muscle cells, with the inner and outer layers oriented longitudinally and the middle one circularly. This orientation is important in determining the bladder's shape and intraluminal pressure. During the storage phase, the detrusor muscle relaxes and elongates to allow the bladder to store urine. When the bladder is full, sensory fibres in the bladder wall send signals to the pontine micturition centre in the brainstem, which regulates the process of bladder filling and voiding.
During urination, the detrusor muscle contracts to push urine out of the bladder and into the urethra. The parasympathetic nervous system stimulates the detrusor muscle to contract, while simultaneously inhibiting the internal urethral sphincter, causing it to relax and allow for bladder emptying. The urethra is composed of smooth muscle, striated muscle, and a lamina propria, which includes a submucosa and a mucosal layer. The external urethral sphincter is composed of striated muscle and is controlled by somatic efferent neurons.
The detrusor muscle can malfunction in two main ways: it can be overactive or underactive. An overactive detrusor muscle contracts when the person is not ready to urinate, causing a severe desire to urinate. If the detrusor muscle is underactive, it may not contract when it should, leading to urinary retention. Abnormalities in the detrusor muscle can lead to urinary retention, incontinence, or a combination of both.
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The bladder is part of the urinary system
The bladder is a key part of the urinary system, which also includes the kidneys, ureters, and urethra. The urinary system is responsible for filtering blood and creating urine as a waste byproduct. The kidneys filter the blood, removing toxins, excess water, and other waste products. The waste products and urine then move from the kidneys through the ureters to the bladder.
The bladder is a hollow, stretchy organ located in the lower abdomen. It acts as a reservoir, storing urine until it leaves the body through the urethra. The bladder has a narrow neck, or internal sphincter, composed of muscle fibres that connect to the urethra. The bladder neck is surrounded by the external sphincter, composed of striated muscle, which provides extra pressure to keep the urethra closed.
The bladder wall is made up of three main layers: the urothelium, or inner lining, which prevents urine from leaking into the body; the lamina propria, a thin layer of loose connective tissue; and the muscularis propria, a thick layer of smooth muscle on the outside of the bladder. The bladder muscle, or detrusor muscle, contracts to expel urine and relaxes to store urine.
Sensory nerves in the bladder wall detect the stretch of the muscle as the bladder fills with urine. These nerves send signals to the brain, indicating the need to urinate. When the bladder is full, the brain signals the bladder muscles to tighten and the sphincter muscles to relax, allowing urine to exit the body through the urethra.
Maintaining a healthy bladder and urinary system is important. Conditions such as urinary tract infections, bladder infections, and kidney stones can affect the urinary system. Pelvic floor exercises, also known as Kegel exercises, can help strengthen the pelvic floor muscles and improve bladder function.
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Frequently asked questions
The bladder is a part of the urinary system and is a temporary storage reservoir for urine. It is a hollow, stretchy organ in the lower abdomen that holds urine until it leaves the body.
The bladder is a hollow, muscular viscus in the pelvis composed of interwoven smooth muscle cells, interspersed with elastin and connective tissues, and lined with transitional epithelium.
The detrusor muscle is composed of three layers of smooth muscle cells. Its primary function is to contract during urination to push urine out of the bladder and into the urethra.
Mechanoreceptors in the bladder wall detect the stretch of the muscle as the bladder fills with urine. These receptors send sensory information to the central nervous system, which controls the release of urine through stimulation of the detrusor muscle.
The neck of the bladder is the constricted part of the bladder that leads to the urethra. It is a narrow group of muscles that connect to the urethra.
