Urinary Incontinence

The urinary bladder, and the urethral sphincter (a muscular band around the urethra that prevents urine flow) are the two lower urinary tract structures, that together with the supporting muscular pelvic floor, are important for control of urination. Their functions are regulated by coordinated peripheral, autonomic (involuntary), and central (voluntary) nervous system control. The two phases of lower urinary tract function—urine storage and voiding (emptying)—are controlled by urine storage and voiding reflexes. In an infant, during urine storage, the bladder relaxes with filling and the sphincter, under autonomic nervous system control, remains closed. At a certain level of filling, a primitive spinal reflex causes sphincter relaxation and simultaneous bladder (detrusor) contraction, resulting in voiding of urine through the urethra. With maturation of the central nervous system pathways, continence is learned, with inhibition of the primitive spinal reflexes by voluntary control through the frontal cerebral cortex.