Detrusor
Pelvic Floor
The bladder wall muscle that contracts to urinate — overactivity causes urge incontinence; underactivity causes urinary retention. It can hold 400-600ml before signaling urgency.
Function
Contracts bladder to expel urine
Origin
Interlacing smooth muscle of bladder wall
Insertion
Bladder neck/trigone region and wall
Innervation
Parasympathetic pelvic splanchnic nerves S2-S4; sympathetic hypogastric input modulates