By perspiration, medicine understands the skin respiration. In addition to the exchange of gases through the skin, this primarily refers to the evaporation of water vapor through the layers of the skin. In terms of gas exchange, perspiration accounts for less than one percent of total respiration for humans.
What is skin respiration?
In medicine, perspiration is skin respiration. In addition to gas exchange through the skin, it refers primarily to the exhalation of water vapor through the layers of the skin. Perspiration or skin respiration is a type of external respiration and thus the diffusion of the respiratory gases oxygen and carbon dioxide. Sometimes this phenomenon is also referred to as perspiratio insensibilis. In this process, the respiratory gases are exchanged with the environment through the surface of the skin. There are organisms whose entire respiration corresponds to external respiration. All anatomical structures of most microorganisms, for example, are located so far on the surface that they can be adequately supplied via perspiration. Evolutionarily, for more complex organisms than microorganisms, skin respiration has proven to be an insufficient respiratory concept to supply all anatomical structures. For this reason, lungs and gills have developed for larger organisms during evolution, which can also adequately supply deeper organs and structures. In humans, skin respiration accounts for less than one percent of total respiration. Without the ability to breathe through the skin, therefore, humans would not suffocate. Only the first millimeter of his tissue would thus not be sufficiently supplied with oxygen. Because of this small physiological effect from the actual gas exchange over the human skin means the perspiration with regard to humans instead of the actual gas exchange often only the evaporation of water over the skin layers.
Function and task
If the evaporation of water via the skin is included under the term perspiration, then perspiration with regard to humans can be said to be a permanent norm process. The skin of every human being therefore continuously exhales water vapor. These evaporation processes are also referred to as diffusion processes. The sweat glands are not involved in this process and the constant loss of water is not consciously perceived. With regard to the amount of perspiration, medicine assumes an average of half a liter to one liter per day. If sweating actually takes place, then instead of perspiration we are talking about transpiration. In this case, the amount of perspiration significantly exceeds the stated 0.5 to one liter, and the loss of water is consciously perceived. Perspiration takes place not only on the externally visible skin, but also in the mucous membranes of the human body. The exact amount of perspiration depends mainly on the environmental conditions and body mass. Breathing frequency, metabolic condition and body temperature also influence perspiration. If the ambient air is fully saturated with water vapor, perspiration does not occur. In addition to the perspiration of water vapor, there is diffusion of respiratory gases. This gas exchange takes place mainly through the pores of the skin. Carbon dioxide is emitted. Oxygen is absorbed. This process is also influenced by factors such as temperature, since temperature determines the speed of the molecules to be exchanged. In this case, gas exchange takes place without a transport medium. This distinguishes skin respiration from lung respiration, in which the blood takes on the role of a transport medium. Skin respiration supplies oxygen to the uppermost 0.5 millimeters of the human body on average. For all deeper tissues, pulmonary respiration and oxygen transport via the blood provides the oxygen supply.
Diseases and ailments
There are known cases in which dancers have died after bronzing the skin. For some time, the impossibility of perspiration after bronzing was assumed to be the supposed cause of death. However, this assumption is wrong. Even after broncation, a person would not suffocate as long as his pulmonary respiration was still functioning. The fact that extensive sealing of the skin can nevertheless be fatal is more likely due to the thermal regulation that is prevented in this way. Thus, the thermocells of the skin continuously absorb external temperatures.The brain compares these temperatures with the body temperatures and then, if necessary, initiates compensatory processes such as cooling sweating in the case of heat or heat-generating cold shivering in the case of cold. Large-scale injury or sealing of the skin can therefore be quite lethal, but the death that occurs as a result would have little to do with perspiration. With regard to perspiration, health complaints may nonetheless occur. Metabolic disorders and metabolic diseases as well as wrong nutritional habits or psychological problems can, for example, manifest themselves in excessive perspiration in the sense of above-average normal evaporation through the skin. However, above-average perspiration can also be genetically determined to a certain extent, especially in the area of the hands and feet. A special case is the so-called hyperhidrosis. This term refers to an overfunction of the sweat glands, which are not actually involved in normal perspiration. Hyperhidrosis can be caused by various factors. Diseases such as tuberculosis, malaria or diabetes and hyperthyroidism are possible causes, as are tumors, medication or menopause. Because of the hyperfunction of the sweat glands, people with hyperhidrosis basically do not perspire at all, but almost exclusively transpire.
