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- Published: 24 Jul 2008
- Uploaded: 23 Aug 2011
- Author: bmedinago
The kidneys perform a number of tasks, such as: concentrating urine, regulating electrolytes, and maintaining acid-base homeostasis. The kidney excretes and re-absorbs electrolytes (e.g. sodium, potassium and calcium) under the influence of local and systemic hormones. pH balance is regulated by the excretion of bound acids and ammonium ions. In addition, they remove urea, a nitrogenous waste product from the metabolism of amino acids. The end point is a hyperosmolar solution carrying waste for storage in the bladder prior to urination.
Humans produce about 2.9 litres of urine over 24 hours, although this amount may vary according to circumstances. Because the rate of filtration at the kidney is proportional to the glomerular filtration rate, which is in turn related to the blood flow through the kidney, changes in body fluid status can affect kidney function. Hormones exogenous and endogenous to the kidney alter the amount of blood flowing through the glomerulus. Some medications interfere directly or indirectly with urine production. Diuretics achieve this by altering the amount of absorbed or excreted electrolytes or osmalites, which causes a diuresis.
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