Kidneys are one organ of the urinary system and the main excretory organ of
human body. They can sustain the stability of the inner environment through
regulating water, osmotic pressure and acid-base balance by discharging waste
products and toxic substances and reabsorbing useful substances in the process
of generating and discharging urine. The substances secreted by kidneys are
related to kinds of human metabolism. Therefore, kidneys are important organ
which keep the normal activities. The following are the main functions of the
kidneys:
1. Maintain water balance. Generating urine is the primary function of
kidneys, through which kidneys can maintain water balance. The generation of
urine comes from blood plasma. The completion of generating urine is composed of
three processes: glomerular filtration, glomerular reabsorption and renal
tubular drainage remit and secretion. In the three processes, except generating
urine, kidneys will also regulate the urine volume according to the volume of
water in the body so as to keep water balance and sustain normal life.
2. Release metabolites and harmful substances such as toxicant, drugs etc.
kidneys filtrate blood plasma through generating urine, which can filter out the
product of metabolism in the body and some other toxicant and chemical drugs
entered into human body and reserve water and nutritional substances. These
waste and harmful substances are discharged through urine, thus guaranteeing the
stability of human inner environment.
3. Keep acid-base balance. Kidneys regulate acid-base balance in human body
through releasing acidic materials, reabsorbing alkaline and alkaline substances
or keep acid-base balance through controlling the discharge volume ratio of
acidic and alkaline substances.
4. Maintain the composition of body fluid and keep a balance of fluid
electrolyte. Kidneys can regulate the substances in human body, such as plasma,
hemalbumin, glucose, amino acid, hormone vitamin, potassium, sodium, chloride
etc and make them exist in human body according to a certain proportion and
density so as to sustain normal activities of human body.
5. Regulate incretion. Kidneys can secrete and synthesize some substances,
which can play a role in regulating human physiological function. Renin and
prostaglandin secreted by kidneys regulate blood pressure and electrolyte
metabolism by influencing the product of ANGII and they can also involve in
hematopoiesis by producing erythropoietic factor and secreting erythrogenin,
stimulate bone marrow erythroid proliferate and differentiate and speed up the
synthesis of hemoglobin. 1, 25 - double hydroxyl vitamin D secreted by kidneys
participates in regulating calcium and phosphate metabolism to sustain the
normal structure and function of the bones.
We could see from the above, kidneys are not only a simple excretory organ,
but also an important organ influencing the inner environment and normal
physiological activities of human. Therefore, kidneys have a significant meaning
for maintaining human life.
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