How to Keep Your Kidneys Healthy as You Age

Although it's been close to eighteen years since I dissected my first cadaver in anatomy class, I still remember being surprised when I got my first glance ata pair of kidneys - they were much smaller than I had expected. Up until that point, I had imagined the kidneys to be quite large, given the amount of work that they are responsible for. Each of your kidneys is about 4 to 5 inches long and about 1 inch thick, weighing in at about 4.5 to 5 ounces. To put it into easy-to-visualize terms, each of your kidneys is a bit larger than a deck of cards. Although your kidneys make up less than 0.5 percent of your total body weight, they receive close to 25 percent of the total amount of blood that your heart pumps while you're resting. Also, your kidneys use up about 20 to 25 percent of your body’s supply of oxygen. Please note: To listen to an audio (mp3) recording of thisarticle, please download and play the following file: How to Keep Your Kidneys Healthy as You Age - Audio File Why do your kidneys – suchsmall organs – receive so much of your blood and oxygen? Because they are responsible for five critical functions: 1. Your kidneys keep your blood clean by filtering it ofwaste products and eliminating these waste products from your body as urine. 2. Your kidneys help maintaina proper balance of fluids throughout your body. 3. Your kidneys secrete a hormone called erythropoietin, which is responsible for stimulating the production of red bloodcells in your bone marrow. 4. Your kidneys produce an enzyme called renin, which is needed to help maintain your blood pressure. 5. Your kidneys convert vitamin D to its most activeform. Public domain diagram of kidneys, view from behind with spine removed - from the 20th U.S. edition of Gray's Anatomy of the Human Body, originally published in 1918Your kidneys lie above yourwaistline, just underneath the surface of your mid/low back region. Although the position of your liver causesyour right kidney to be slightly lower in your abdominal cavity than your left kidney, both kidneys arepartially protected by the lower part of your ribcage. With every beat of your heart, large amounts of blood are delivered to your kidneys via your renal arteries. Inside your kidneys, your renal arteries split up into a number of smaller branches that distribute blood to your nephrons, which are the microscopic processing units of your kidneys; you have about a million nephrons per kidney. Within each nephron, there are specialized beds of capillaries (even smaller blood vessels) called glomeruli. The glomeruli filteryour blood, and pass the filtrate on to a series of specialized tubules that are collectively known as the renal tubule – it’s in the renal tubule where urine is created. The process of creating urine is complex, but in essence, what happens is this: about a fifth of the blood that passes through each of your kidneys gets filtered by your glomeruli to enter your the renal tubules;the stuff that passes through is referred to as filtrate, which includes wastematerials, water, chloride ions, sodium ions, bicarbonate ions, glucose, potassium ions, urea, uric acid, and protein. As the filtrate travels through the renal tubule, about 99 percent of it is reabsorbed into your blood circulation - this number alone gives you a good idea of how hard your kidneys work to produce urine; of the approximately 40 gallons (150 litres) of filtrate that enters your kidneys on a daily basis, only about 1 to 2quarts (1 to 2 litres) turns into urine. The 99 percent that is reabsorbed into your circulation is how your kidneys help to maintain your body’s fluid compositionand pH level