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    How the Kidney Works

    The kidneys are two vital organs that perform many functions to keep the blood clean and chemically balanced. They are two fist-sized, bean shaped organs located near the middle of the back, just below the rib cage. Each day, the kidneys process approximately 200 quarts of blood, removing about two quarts of waste products and extra water from the body. The waste and extra water become urine. The urine flows to the bladder through tubes called ureters.

    Normal breakdown of tissues and food creates the waste in the blood. If the waste was not removed, it would build up in the blood and damage the body. Inside the kidney are tiny filtering units called nephrons. There are about a million nephrons in each kidney. Inside each nephron is a tiny blood vessel called a glomerulus. The glomerulus intertwines with a tiny urine-collecting tube called a tubule. The tubules receive waste and chemicals the body will use.

    Anterior view of the circulatory system showing the heart, kidney arteries and veins, right kidney, left kidney, abdominal aorta, right ureter, left ureter, bladder, and urethra. Anatomy of the Kidney. Enlarged cut-away view of the left kidney showing the flow of fresh blood carrying oxygen to the kidney through the kidney artery, flow of old blood carrying carbon dioxide away from the kidney through the kidney vein, capsule, cortex, ureter, urine exiting kidney, and hilum. Blood Flow within the Kidney. Enlargement of the kidney tissue showing the flow of blood carrying oxygen to the nephrons and blood carrying carbon dioxide away from the nephrons.

    Medical Illustration Copyright © 2007 Nucleus Medical Art, All rights reserved.

    The kidneys remove chemicals including sodium, phosphorus and potassium, and release them back into blood, returning them to the body. The kidneys regulate the body’s level of these substances so they do not reach harmful levels.

    The kidneys also release the following three important hormones:
    • Erythropoietin (eh-RITH-ro-POY-eh-tin), which stimulates the bone marrow to make red blood cells

    • Renin (REE-nin), which regulates blood pressure

    • Calcitriol (kal-suh-TRY-ul), the form of vitamin D which helps maintain calcium for bones and for normal chemical balance in the body

    About California Pacific Medical Center

    California Pacific Medical Center, part of the Sutter Health network, offers kidney, pancreas, liver and heart transplantation as part of our Barry S. Levin, MD Department of Transplant.

    Kidney & Pancreas Transplant Program
    California Pacific Medical Center
    2340 Clay Street
    San Francisco, CA 94115
    Tel. 415-600-1700

    Outreach locations available throughout Northern California and in Reno.