The kidneys Kidneys The kidneys are bean-shaped organs that figure prominently in the urinary tract. Each is about 4 to 5 inches (12 centimeters) long and weighs about one third of a pound (150 grams). One lies... read more filter and cleanse the blood. They also maintain the body’s balance of water About Body Water Water accounts for about one half to two thirds of an average person’s weight. Fat tissue has a lower percentage of water than lean tissue and women tend to have more fat, so the percentage... read more , dissolved salts (electrolytes Overview of Electrolytes More than half of a person's body weight is water. Doctors think about water in the body as being restricted to various spaces, called fluid compartments. The three main compartments are Fluid... read more , such as sodium Overview of Sodium's Role in the Body Sodium is one of the body's electrolytes, which are minerals that the body needs in relatively large amounts. Electrolytes carry an electric charge when dissolved in body fluids such as blood... read more , potassium Overview of Potassium's Role in the Body Potassium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood. (See also Overview of Electrolytes.) Most of the body’s... read more , and calcium Overview of Calcium's Role in the Body Calcium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but most of the body's calcium is uncharged. (See also... read more ), and nutrients in the blood.
The kidneys begin these tasks by filtering the blood as it flows through microscopic tufts of blood vessels with small pores (called glomeruli). This process moves a large amount of water and electrolytes and other substances into small tubules. The cells lining these tubules reabsorb and return needed water, electrolytes, and nutrients (such as glucose and amino acids) to the blood. The cells also move waste products and drugs from the blood into the fluid (which becomes urine) as it flows through the tubules.
The cells lining the tubules add hormones that maintain blood supply (erythropoietin), blood pressure, and electrolyte balance and also make an enzyme that activates vitamin D (calcitriol). When in its active form, calcitriol is able to help regulate calcium and phosphorus and maintain healthy bone.
Viewing the Urinary Tract
Disorders that interfere with the function of the cells lining the kidney's tubules are called tubular disorders Introduction to Disorders of Kidney Tubules The kidneys filter and cleanse the blood. They also maintain the body’s balance of water, electrolytes (such as sodium, potassium, bicarbonate, and chloride), and nutrients in the blood. The... read more . Some tubular disorders are hereditary, so they are present at birth (congenital). Of these congenital tubular disorders, some are detected in the first year of life, and others are not obvious until years later.
Congenital tubular disorders include the following: