Functions of the Urinary System
One of the major functions of the Urinary system is the process of
excretion. Excretion is the process of eliminating, from an organism,
waste products of metabolism and other materials that are of no use.
The urinary system maintains an appropriate fluid volume by regulating
the amount of water that is excreted in the urine. Other aspects of its
function include regulating the concentrations of various electrolytes
in the body fluids and maintaining normal pH of the blood. Several body
organs carry out excretion, but the kidneys are the most important
excretory organ. The primary function of the kidneys are to maintain a
stable internal environment (homeostasis) for optimal cell and tissue
metabolism. They do this by separating urea, mineral salts, toxins, and
other waste products from the blood. They also do the job of conserving
water, salts, and electrolytes. At least one kidney must function
properly for life to be maintained. Six important roles of the kidneys are:
Regulation of plasma ionic composition. Ions such as sodium,
potassium, calcium, magnesium, chloride, bicarbonate, and phosphates
are regulated by the amount that the kidney excretes.
Regulation of plasma osmolarity. The kidneys regulate osmolarity because they have direct control over how many ions and how much water a person excretes.
Regulation of plasma volume. Your kidneys are so important
they even have an effect on your blood pressure. The kidneys control
plasma volume by controlling how much water a person excretes. The
plasma volume has a direct effect on the total blood volume, which has
a direct effect on your blood pressure. Salt(NaCl)will cause osmosis to
happen; the diffusion of water into the blood.
Regulation of plasma hydrogen ion concentration (pH). The
kidneys partner up with the lungs and they together control the pH. The
kidneys have a major role because they control the amount of
bicarbonate excreted or held onto. The kidneys help maintain the blood
Ph mainly by excreting hydrogen ions and reabsorbing bicarbonate ions
as needed.
Removal of metabolic waste products and foreign substances from the plasma.
One of the most important things the kidneys excrete is nitrogenous
waste. As the liver breaks down amino acids it also releases ammonia.
The liver then quickly combines that ammonia with carbon dioxide,
creating urea which is the primary nitrogenous end product of
metabolism in humans. The liver turns the ammonia into urea because it
is much less toxic. We can also excrete some ammonia, creatinine and
uric acid. The creatinine comes from the metabolic breakdown of creatine phospate (a high-energy phosphate in muscles). Uric acid
comes from the break down of necloetides. Uric acid is insoluble and
too much uric acid in the blood will build up and form crystals that
can collect in the joints and cause gout.
Secretion of Hormones The endocrine system has assistance
from the kidney's when releasing hormones. Renin is released by the
kidneys. Renin leads to the secretion of aldosterone which is released
from the adrenal cortex. Aldosterone promotes the kidneys to reabsorb
the sodium (Na+) ions. The kidneys also secrete erythropoietin when the
blood doesn't have the capacity to carry oxygen. Erythropoietin
stimulates red blood cell production. The Vitamin D from the skin is
also activated with help from the kidneys. Calcium (Ca+) absorption
from the digestive tract is promoted by vitamin D.
CC: Chapter Check: Name the role of the kidneys and how they work?
| 
