Muscle
Detrusor muscle
The bladder's distensible smooth-muscle wall
High-yield
Parasympathetic acetylcholine drives contraction mainly through M3 receptors. Beta-3 receptor activation contributes to relaxation and storage function.
Overview
Interlacing smooth-muscle bundles form the detrusor across the bladder wall. They change shape during low-pressure storage and contract together during voiding. Longitudinal and circular orientations can be recognized, but they do not form sharply separate layers everywhere.
Reference facts
- Origin
- Forms a continuous smooth-muscle coat across the bladder apex, body and base, without skeletal-muscle-style origins.
- Insertion
- Bundles converge and interweave near the outlet, with continuity into bladder-neck and urethral smooth muscle.
- Innervation
- Sacral parasympathetic fibers through pelvic plexuses promote contraction; thoracolumbar sympathetic pathways contribute to storage regulation.
- Action
- Generates voiding pressure when the outlet relaxes and accommodates increasing volume during filling.
- Blood supply
- Vesical branches of the internal iliac system, with vaginal and other regional contributions in females.
Clinical correlation
Involuntary filling-phase contractions may contribute to urgency and urge leakage, although symptoms and measured detrusor overactivity are not identical. Chronic outlet obstruction can produce muscle thickening and trabeculation; later emptying impairment is possible but not inevitable.
Frequently asked questions
What does the detrusor muscle do?
The detrusor muscle generates voiding pressure when the outlet relaxes and accommodates increasing volume during filling.
What nerve innervates the detrusor muscle?
Sacral parasympathetic fibers through pelvic plexuses promote contraction; thoracolumbar sympathetic pathways contribute to storage regulation.
Where does the detrusor muscle attach?
Origin: Forms a continuous smooth-muscle coat across the bladder apex, body and base, without skeletal-muscle-style origins. Insertion: Bundles converge and interweave near the outlet, with continuity into bladder-neck and urethral smooth muscle.
What is the blood supply of the detrusor muscle?
The detrusor muscle is supplied by the vesical branches of the internal iliac system, with vaginal and other regional contributions in females.