The kidneys serve as the body’s primary waste filtration and disposal system. Up to one-third of the blood pumped by the heart flows through the kidneys, where it is filtered before continuing to the rest of the body. 

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The urinary bladder is a hollow, flexible organ that acts as the body’s reservoir for urine. Once urine is produced by the kidneys, it travels through the ureters into the bladder, where it is held until it is ready to be expelled through the urethra. The bladder plays a crucial role in regulating and postponing urination, allowing most people to empty their bladder just a few times a day rather than continuously releasing small amounts of urine.