Click to expand Tap to zoom Bladder Organ by Giant Microbes Sold in Units of: 4 Current stock: 53 Sale SKU GMO-3041 4 8 12 16 20 24 28 32 36 10+ Quantity Quantity Add to cart The bladder is a hollow muscular bag that lies in the pelvic cavity. This organ’s main function is to store urine produced in the kidneys. An average bladder can hold 2.5 cups, or 600 milliliters, of urine!