When we eat, our body absorbs the nutrients from our food and processes and eliminates what it doesn’t need. Some wastes enter the bloodstream and are filtered out through the kidneys. The nephrons within the kidneys are the key to filtering; each kidney contains about a million nephrons. A nephron is made up of a coil of blood vessels called a glomerulus (Latin for “little ball”) attached to a tubule. The glomeruli allow certain substances, such as water and urea to pass from the blood into the tubules. Inside the tubules, some of the water, salt and other substances are re-absorbed into the body to maintain the proper chemical balance. So, while our kidneys filter about 200 quarts of blood each day, only about 2 quarts leave the body as urine, passing from the winding tubules to the ureters and into the bladder.