Picture of Kidneys
The kidneys are two organs that lie on either side of the spine just under the rib cage. Kidneys serve many important functions including filtering blood, controlling electrolyte balance, and producing hormones. Nephrons are the small filtering units in the kidneys. Nephrons filter wastes and excess fluid out of the blood. Concentrated waste (urine) travels from the kidneys down tubes called the ureters and into the bladder. The kidneys produce approximately 1 to 2 quarts of urine per day.
Text Reference: "The Kidneys and How They Work." National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC).