Detrusor muscle

Muscle of the urinary bladder

Detrusor muscle

The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle fibers arranged in a spiral, longitudinal, and circular pattern. This muscle is crucial for the storage and expulsion of urine from the bladder.

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Diagram of the bladder showing the detrusor muscle

Anatomy

The detrusor muscle is located in the wall of the bladder and is composed of three layers of smooth muscle fibers. These fibers are arranged in a complex manner to allow the bladder to expand and contract efficiently. The outer and inner layers are longitudinal, while the middle layer is circular.

Function

The primary function of the detrusor muscle is to contract during micturition (urination) to expel urine from the bladder. During the storage phase, the detrusor muscle remains relaxed to allow the bladder to fill with urine. The coordination of the detrusor muscle with the internal urethral sphincter and external urethral sphincter is essential for normal urinary function.

Innervation

The detrusor muscle is innervated by the autonomic nervous system. The parasympathetic nervous system stimulates the detrusor muscle to contract, facilitating urination. The sympathetic nervous system helps to relax the detrusor muscle during the storage phase.

Clinical significance

Dysfunction of the detrusor muscle can lead to various urinary disorders, such as overactive bladder, urinary incontinence, and urinary retention. Overactivity of the detrusor muscle can cause frequent and urgent urination, while underactivity can lead to difficulty in emptying the bladder.

Related pages

• Urinary bladder
• Micturition
• Urinary incontinence
• Overactive bladder