Urinary Bladder

About the Urinary Bladder

The urinary bladder is a hollow muscular organ in the pelvis that stores urine produced by the kidneys. It holds approximately 300 to 500 mL comfortably, with the urge to void felt at 150 to 250 mL. The bladder wall has the detrusor muscle smooth muscle that contracts during urination. The trigone is a triangular area at the bladder base with the two ureteral orifices and the urethral orifice, clinically important as a fixed landmark for cystoscopy. The internal urethral sphincter smooth muscle involuntary is at the bladder neck, preventing retrograde ejaculation in males. The external urethral sphincter skeletal muscle voluntary is within the urogenital diaphragm. The micturition reflex: bladder filling stretches the detrusor, activating stretch receptors via pelvic splanchnic nerves parasympathetic S2-S4, causing detrusor contraction and internal sphincter relaxation simultaneously. The external sphincter is voluntarily relaxed. Pontine micturition center coordinates the reflex. Incontinence types include stress cough, sneeze, urge overactive bladder, overflow obstruction or neurogenic, and functional. BPH commonly causes urinary symptoms in older men. Urinary retention, the inability to empty the bladder, is managed with catheterization.