Which structure in the urinary system stores urine until excretion?

The bladder is the structure in the urinary system that stores urine until it is ready to be excreted. It is a muscular sac located in the pelvis and has the ability to expand and contract. As the bladder fills with urine produced by the kidneys, stretch receptors in the bladder wall send signals to the brain, indicating the need to urinate. When the brain receives these signals, voluntary and involuntary muscle contractions coordinate to allow urine to be expelled from the bladder through the urethra during the process of urination.

In contrast, the kidneys are responsible for filtering blood, removing waste products, and producing urine, but they do not store urine. The ureters serve as conduits to transport urine from the kidneys to the bladder, and the urethra is the tube through which urine exits the body from the bladder. While all these structures play important roles in the urinary system, the bladder is specifically designated for the storage of urine.