FUNCTIONS OF THE KIDNEYS
[photo credit: Michal]
The kidneys perform a number of functions, among which are:
1. Osmoregulation: Osmoregulation is defined as the process whereby an animal regulates the balance between water and salts in its body fluids. The body does not have room for excess or shortage of water or salt, hence the need to always maintain their levels in the fluid.
Osmoregulation in Man
The kidneys carry out osmoregulation in man. When the osmotic concentration of blood is higher than that of cell content by means of sugar, mineral salts, amino acids and other plasma solutes, the kidneys extract these substances from the blood or body cells and absorb more water.
When these substances are present in small quantity in the blood, they create higher osmotic pressure in the body cells, thus decreasing the osmotic concentration of the blood, and the kidneys extract more water than usual.
By the action of Anti-Diuretic Hormone (ADH), more concentrated urine is produced, thus keeping the osmotic concentration of of blood and cells fairly constant.
Osmoregulation in man, especially loss of water, is usually carried out through sweating by skin and exhalation by the lungs.
2. Excretion: The kidneys are also involved in the removal of metabolic waste from the body in form of urine. The proces involved in the formation of urine occurs in three phases, which are:
- ultra-filtration
- selective reabsorption
- hormonal secretion
3. Maintenance of acid-base balance: The kidneys also maintain the acid-base balance in the body. When the body fluids become acidic, i.e, the concentration of acids becomes more than that of bases, more acid is excreted by the kidneys with the urine. Excessive loss of bases is prevented at the same time by the kidneys. If the concentration of base becomes higher, more salts would be excreted with the urine.
CONDITIONS AFFECTING THE FUNCTIONING OF THE KIDNEYS
There are different conditions or factors affecting that affect teh functioning of the kidneys. These include:
- environmental temperature
- drugs
- habitats
- diseases
1. Environmental temperature: This affects the functioning of the kidneys. On cold days, there is every tendency to urinate more than we do on hot days. On hot days, much water is lost by sweating, while on cold days, very little or no water is lost by sweating, hence more of the excess water in the body is lost through the kidneys. Under this condition, the kidneys are under stress as the have to remove excess water, salts and other waste products from the bod.
2. Drugs: Some drugs taken by human beings do affect the functioning of the kidneys. Among the essential drugs which affect the kidney are diuretics. These are usually taken to get rid of excess water out of the body.
3. Habitats: Habitats, especially aquatic habitats, do have some effects on the functioning of the kidneys. In fresh water habitats, the animals live in an environment which is called hypotonic to their body fluid. As a result, fresh water animals experience a constant inflow of water into their bodies.
The fresh water animals are able to solve this problem of excessive intake of water by excreting salts and other nitrogenous wastes through the urine, thereby maintaining a normal salt and water balance in the body.
In marine habitats, the animals live in an environment which is hypertonic to their body fluid, i.e, the body gluid is less concentrated than its water environment. As a result, the marine animals experience constant outflow or loss of its body water to the surrounding saline or salty water.
These marine animals are able to solve this excessive loss of water by either the reabsorption of urea back into the blood, thereby leading to an increase in body salts and making the body fluid to have a high concentration or they drink plenty of salt water so that the concentration of blood fluid is raised.
4. Diseases: Diseases, such as nephritis, kidney stones, diuresis, dropsy, etc can affect the normal functioning of the kidneys.
Also read: Diseases of the kidneys, their effects and remedies
Also read: Diseases of the kidneys, their effects and remedies
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