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Chapter 16
Urine Formation
Term | Definition |
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Three major steps of urine formation | Glomerular filtration, tubular reabsorption, and tubular secretion. |
Glomerular filtration | Blood is pushed into the glomerulus and small molecules are filtered through the capillaries into the glomerular capsule. |
Glomerular filtrate | The glomerular filtrate is all of the molecules separated from the blood during glomerular filtration, this includes water, nitrogenous wastes, small nutrients, salts, creatinine, and urochrome. |
Tubular reabsoprtion | Molecules such as nutrients and salts are reabsorbed into the blood from the convoluted tubules and the ascending limb of the loop of Henle. Some molecules are absorbed passively while others are done actively. |
Molecules reabsorbed | 99% of the water, 99.5% of the sodium, 100% of the glucose, and 44% of the urea filtered by the kidneys is reabsorbed by the blood during tubular reabsorption. |
Tubular secretion | The process of active transport that removes waste from the blood and deposits the wastes directly into the tubules of a nephron. These substances include hydrogen ions, potassium ions, creatinine, and drugs. |
Urine/Waste Produced | Urine contains (1) substances that have gone through glomerular filtration and were not reabsorbed, and (2) substances that have undergone tubular secretion. |