hollow muscular organ that stores urine
Urinary bladder. The urinary bladder is a hollow muscular organ in many animals, that collects and stores urine from the kidneys before disposal by urination. In the human the bladder is a hollow muscular, and distensible (or elastic) organ, that sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra. The typical human bladder will hold between 300 and 500 mL (10.14 and 16.91 fl oz) before the urge to empty occurs, but can hold considerably more.