The process of excretion involves the lungs, kidneys, and skin removing waste from the body. The urinary system, including the kidneys, ureters, bladder, and urethra, filters liquid waste from the blood to produce urine, which is stored in the bladder and expelled through urination. The kidneys filter blood multiple times per day to remove waste and produce urine for excretion.

4. During circulation, blood passes through the kidneys in order to deposit used and unwanted water, minerals, and a nitrogen-rich molecule called urea. The kidneys filter the wastes from the blood, forming a liquid called urine. The kidneys send the urine into the bladder along two separate tubes called ureters. The bladder stores the urine until muscular contractions force the urine out of the body through the urethra.

7. The kidneys filter that blood as many as 400 times a day! More than 1 million tiny filters inside the kidneys remove the waste. These filters, called nephrons are so small you can see them only with a high-powered microscope. Each day, your kidneys produce about 1.5 litres of urine. All of it needs to be removed from your system. This occurs through urination.