What is the name of the round saclike organ in the renal system that serves as a reservoir for urine?

The bladder is the round saclike organ in the renal system specifically designed to store urine before it is expelled from the body. It has a muscular wall that allows it to expand as it fills with urine and contract during urination, facilitating the effective release of urine from the body. This ability to serve as a reservoir is crucial for maintaining urinary control and proper elimination, as it permits the body to manage urination at convenient times.

Other structures mentioned in the options have different functions. The liver is involved in detoxification, metabolism, and the production of bile but does not play a role in urine storage. The kidneys are responsible for filtering blood to produce urine, but they do not hold urine for expulsion. The ureters are tubes that transport urine from the kidneys to the bladder but do not store urine themselves. Thus, the bladder's unique structure and function make it the correct answer in this context.