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The bladder is an organ of the urinary system, situated in the pelvic cavity. It is a temporary storage reservoir for urine. 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 bladder or detrusor muscle is composed of three layers of typical smooth muscle cells, where the inner and outer layers are oriented longitudinally and the middle one circularly. The external urethral sphincter is made of skeletal muscle and is under voluntary control.
| Characteristics | Values |
|---|---|
| What is it? | A temporary storage reservoir for urine |
| Location | In the pelvic cavity, posterior to the symphysis pubis, and below the parietal peritoneum |
| Composition | Three layers of smooth muscle cells with the inner and outer layers oriented longitudinally and the middle one circularly |
| Control | Autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system |
| Function | Receives input from the nervous system to relax and store urine or contract and expel urine |
| Related issues | Stress urinary incontinence, urge incontinence, bladder overactivity, urinary retention |
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What You'll Learn
- The bladder is a hollow, muscular organ in the pelvis
- The bladder is part of the urinary system and acts as a temporary store for urine
- The bladder is made up of detrusor muscle, which is smooth muscle
- The detrusor muscle contracts during urination and relaxes to hold urine
- The urethral sphincter muscles control the flow of urine
The bladder is a hollow, muscular organ in the pelvis
The bladder is composed of interwoven smooth muscle cells, with elastin and connective tissues, and is lined with transitional epithelium. The outer layer of the bladder, known as the muscularis propria, consists 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 for maintaining the bladder's shape and intraluminal pressure. The bladder also contains specialised smooth muscle fibres, known as the detrusor muscle, which contract during micturition.
The detrusor muscle plays a crucial role in the storage and emptying of urine. It receives signals from both the sympathetic and parasympathetic nervous systems, which control the relaxation and contraction of the muscle. The sympathetic nervous system causes the detrusor muscle to relax, promoting urine retention, while the parasympathetic nervous system stimulates contraction of the muscle, leading to micturition. The somatic nervous system also plays a role in providing voluntary control over micturition.
The urethra, which is also composed of smooth muscle, works in conjunction with the bladder to control the outflow of urine. The urethral sphincters, composed of the internal and external sphincter muscles, seal the urethra shut to prevent the release of urine. The external sphincter is made of skeletal muscle and is under voluntary control, while the internal sphincter is made of smooth muscle and functions involuntarily. Together, these muscles and the detrusor muscle ensure the proper storage and release of urine, maintaining urinary continence.
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The bladder is part of the urinary system and acts as a temporary store for urine
The bladder is part of the urinary system, which is the body's drainage system for removing urine. The urinary system removes waste and extra fluid from the body through a series of organs, ducts and tubes. The kidneys, ureters, bladder and urethra make up the urinary system.
The bladder acts as a temporary store for urine. It is a hollow, muscular organ in the pelvis, composed of interwoven smooth muscle cells, interspersed with elastin and connective tissues, and lined with transitional epithelium. The bladder sits between the hip bones and is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours.
The bladder is divided into the bladder body and the base. The bladder body is located above the ureteral orifices, and the base consists of the trigone and the urethrovesical junction. The bladder neck, also known as the internal sphincter, is a funnel-like structure formed by the condensation of the bladder's muscle fibres. The internal sphincter controls involuntary urine flow from the bladder to the urethra. The external sphincter, meanwhile, controls voluntary urine flow from the bladder to the urethra.
The bladder receives input from both the autonomic (sympathetic and parasympathetic) and somatic arms of the nervous system. The sympathetic arm causes relaxation of the detrusor muscle, promoting urine retention, while the parasympathetic arm causes contraction of the detrusor muscle, stimulating micturition. The somatic arm innervates the external urethral sphincter, providing voluntary control over micturition.
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The bladder is made up of detrusor muscle, which is smooth muscle
The bladder is a hollow, muscular organ in the pelvis that collects and stores urine. It is part of the urinary system and is situated anteriorly in the pelvic cavity.
The bladder is made up of detrusor muscle, which is a smooth muscle. The detrusor muscle is located within the walls of the bladder and is composed of smooth muscle fibres that are longitudinal and circular. The layers of the detrusor muscle start longitudinally in the inner layer, become circular in the middle layer, and then longitudinal again in the outer layer. This orientation is important as it determines the bladder's shape and intraluminal pressure.
The detrusor muscle contracts during urination to push urine out of the bladder and into the urethra. It is under autonomic control and receives input from both the sympathetic and parasympathetic nervous systems. When the bladder is full of urine, the M3 receptors located within the bladder become stretched and stimulated, leading to the contraction of the detrusor muscle for urination. At the same time, the parasympathetic fibres inhibit the internal urethral sphincter, causing relaxation and allowing for bladder emptying.
The detrusor muscle relaxes to allow the storage of urine in the bladder. When the bladder is filling with urine, the detrusor muscle is kept relaxed via sympathetic branches from the inferior hypogastric plexus. The sympathetic nervous system also stimulates the beta-3 receptors through the adenylyl cyclase-cAMP pathway in the bladder, causing relaxation of the detrusor muscle.
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The detrusor muscle contracts during urination and relaxes to hold urine
The bladder is an organ of the urinary system, situated in the pelvic cavity. It collects and stores urine until it is time to urinate. The bladder is composed of smooth muscle cells, known as the detrusor muscle, which is located within its walls. The detrusor muscle contracts during urination to push urine out of the bladder and into the urethra. This contraction is stimulated by the parasympathetic nervous system, specifically acting on postganglionic M3 receptors. The detrusor muscle is also under the control of the autonomic system, which includes both the sympathetic and parasympathetic nervous systems.
During the storage phase, the detrusor muscle relaxes to allow the bladder to fill with urine. This relaxation is maintained through sympathetic branches from the inferior hypogastric plexus. The smooth muscle fibres of the detrusor muscle are oriented in multiple directions, allowing the bladder to stretch and accommodate more urine. This stretching is sensed by bladder afferent neurons, which signal to the brain that the bladder is full.
The urethra is the tube that connects the bladder to the outside and is composed of smooth muscle, striated muscle, and a lamina propria. The urethral sphincters, composed of skeletal muscle, control the exit of urine from the bladder through the urethra. There are two urethral sphincters: the internal urethral sphincter, composed of smooth muscle, and the external urethral sphincter, composed of skeletal muscle. The internal sphincter is involuntary and functions to prevent the involuntary flow of urine. The external sphincter, on the other hand, is under voluntary control, allowing for conscious control over urination.
Any damage to the detrusor muscle or the urethral sphincters 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. Similarly, weak pelvic floor muscles, intrinsic sphincter damage, or nerve damage can lead to stress urinary incontinence, where the urethral sphincter does not close fully.
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The urethral sphincter muscles control the flow of urine
The bladder is an organ of the urinary system, situated in the pelvic cavity. It collects and stores urine. The bladder is a hollow, muscular organ, composed of interwoven smooth muscle cells, interspersed with elastin and connective tissues, and lined with transitional epithelium. The portion of the bladder muscle that contracts to expel urine is also known as the detrusor.
The urethra allows urine to exit the body and prevents leakage during storage by generating higher pressure than the bladder. The urethra is composed of smooth muscle, striated muscle, and a lamina propria, which has a submucosa and a mucosal layer. The urethral sphincters are two muscles that control the exit of urine from the bladder through the urethra. The two muscles are the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.
The external urethral sphincter originates at the ischiopubic ramus and inserts into the intermeshing muscle fibres from the other side. It is controlled by the deep perineal branch of the pudendal nerve. Activity in the nerve fibres constricts the urethra. The external urethral sphincter is made of skeletal muscle, and therefore, it is under voluntary control of the somatic nervous system.
The internal urethral sphincter is located at the bladder's inferior end and the urethra's proximal end at the junction of the urethra with the urinary bladder. The internal sphincter is a continuation of the detrusor muscle and is made of smooth muscle, therefore it is under involuntary or autonomic control. The internal urethral sphincter controls involuntary urine flow from the bladder to the urethra. In males, it also prevents the flow of semen into the bladder during ejaculation.
Any damage to these muscles can lead to urinary incontinence. Weak pelvic floor muscles, intrinsic sphincter damage, or damage to the surrounding nerves and tissue can make the urethral sphincter incompetent, and subsequently, it will not close fully, leading to stress urinary incontinence.
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Frequently asked questions
The bladder is an organ of the urinary system, located in the pelvic cavity. It collects and stores urine.
The bladder is a hollow, muscular viscus in the pelvis composed of interwoven smooth muscle cells, interspersed with elastin and connective tissues. The bladder is not skeletal muscle.
The bladder muscle, also known as the detrusor muscle, contracts during urination to release urine and relaxes to allow the storage of urine in the urinary bladder.
The urethral sphincters are two muscles that control the exit of urine from the bladder through the urethra. The external urethral sphincter is made of skeletal muscle and is under voluntary control. The internal urethral sphincter is made of smooth muscle and is under involuntary or autonomic control.
