By excretion, physicians mean the release of certain metabolic products into the environment. Without excretion, the balance in metabolism would be disturbed and poisoning by metabolic products such as ammonia could occur. Disturbed excretion is present, for example, in the group of storage diseases.
What is excretion?
Excretion is the excretion of unwanted or unusable metabolites, such as urea, via the kidneys and bladder. Excretion is the elimination of unwanted or unusable metabolites. Defecation, as well as the excretion of dissolved constituents and the release of gaseous constituents, all fall under the heading of excretion. During defecation, indigestible food components are excreted, and components dissolved by micturition leave the body via urine. The products of these two types of excretion are collectively referred to as excreta. Gases released rectally by flatulence and respiratory gases can also count as excretions. Six different excretory pathways are available in the human organism: the lungs, the skin, the kidney, the liver, the colon, and the mammary gland. In the narrower sense, however, only defecation and flatulence are counted as excretions. Excretion takes place not only in the human and animal organism, but also in the plant organism. As a rule, this excretion takes place through special pathways and refers to the excretion of all substances that are harmful to the plant organism.
Function and task
During excretion, by and large, all metabolic products that disturb the balance of metabolism are excreted. From the human organism must be eliminated with this goal primarily all nitrogenous metabolic products. Excreted products for humans are therefore primarily solid, liquid or gaseous products that contain nitrogen and could thus throw the metabolism out of balance. In amino acid metabolism and nucleic acid metabolism, ammonia is the most important waste product. In most animals, this ammonia is first converted into urea or uric acid, because in its original form the substance would be toxic to the organism. This is especially true of land-dwelling creatures. Because uric acid is difficult to dissolve in water, it is excreted as a crystalline substance or as a pasty substance with the excrement. Unlike uric acid, urea is water-soluble and is the major excretory product of vertebrates. When urea accumulates, osmotic pressure increases in the organism. Therefore, larger amounts of urea must first be dissolved in water. Most terrestrial vertebrates are capable of concentrating urine. In their liver, urea is produced as part of the urea cycle, in which carbon dioxide plays an important role as a starting material in addition to ammonia. From the liver, urea reaches the kidneys and from there it moves on to the bladder and leaves the body. In addition to ammonia, ammonium and creatinine are also substances of excretion and are excreted by humans primarily through the urine. Accompanying substances of excretion are generally water and lubricants, which migrate into the excreta primarily for intestinal passage. In addition to nitrogen excretion, the excretion of salts is also important for the human body. To regulate osmosis, the organism must engage in selective excretion of salts and thus adjust the salt concentration. This selective excretion occurs primarily through the urine. In smaller quantities, the excretion of salts also takes place through sweat. In this way, the body prevents the concentration of dissolved substances from becoming too high and establishes a tolerable water content. In this way, excretion serves many purposes for humans. Detoxification, osmoregulation and control of acid-base balance are among the most important, but excretion is also involved in thermoregulation in the sense of sweating.
Diseases and ailments
Each excretory pathway can be affected by disease. For example, dysfunction may be present in the sweat glands, resulting in hyperhidrosis, hypohidrosis, anhidrosis, bromhidrosis, or chromhidrosis. Hyperhidrosis is the excessive activity of the sweat glands, which can be either chronic or acute. Brain diseases often cause such hyperactivity.Especially if the excessive sweating is predominantly local, innervation damage of certain glands may be the cause. In anhidrosis, the opposite phenomenon is present. Thus, sweat production is greatly reduced in anhidrosis. This type of complaint is usually symptomatic and thus occurs in the context of a certain primary disease, for example, accompanying tuberculosis. In bromhidrosis, the sweat takes on an abnormally strong odor, and in chromhidrosis, it changes color. Both manifestations usually refer to primary diseases, such as syphilis. Excretory diseases can also appear as storage diseases, such as in Wilson’s disease. In this disease, the body stores copper substances in the organs, damaging the liver to the point of cirrhosis. The group of lysosomal storage diseases also results in impaired excretion and is usually associated with enzymatic defects. An excess of uric acid, on the other hand, occurs in gout, for example. Equally well, all kidney, liver and intestinal diseases can lead to complaints of excretion. Likewise, symptomatic excretory dysfunction often occurs in diseases of the nervous system, due to nervous system dysregulation.
