ABSTRACT
Toxins are generally cleared from the body either by the kidney or by the liver and gastrointestinal tract. The kidney is required to maintain total body salt, water, potassium, and acid-base balance, while excreting waste products and toxins. The kidney is therefore responsible for preserving the body’s internal environment. The kidney uses three general mechanisms to accomplish these goals: glomerular filtration, tubular reabsorption, and tubular secretion. A basic understanding of these processes is important because they can affect the excretion or retention of various toxins. The movement of water and solute across the glomerular capillary wall to form an ultrafiltrate of plasma is called glomerular filtration; the rate at which this occurs is called the glomerular filtration rate (GFR). The movement of a substance from tubular fluid back into the plasma is called tubular reabsorption and results in retention of that substance within the body. The movement of a substance from plasma into the tubular fluid is called tubular secretion and results in excretion of that substance into the urine.
