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Evolutionary fundamentals of lungs and the body tissues and systems interaction

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N.I. Tsirelnikov

Ph. D. in medical sciences, professor, head of the human evolution and reproductive health department at the Scientific Centre for clinical and experimental medicine at the Siberian Branch of the Russian Academy of Medical Sciences

Breathing is the most significant limiting factor in the life of mammals, since for a long evolution period higher organisms have in principle lost the ability to deposit oxygen. Mammals can do without food for quite a while - about 30-45 days, without water - 2-3 days, as for oxygen, without it irreversible alterations in the cerebrium cells set in already in 4-5 minutes. Oxygen began to form on the Earth about 2 billion years ago and the first creatures, primitive life forms were anaerobes, at that, i.å. they lived in an oxygen-free medium. It is believed that mitochondria that are responsible for energy supply of the modern cells represented, as it were, a separate living structure, which was symbiotically assimilated by cellular life forms, undergoing evolution at the time. The higher on the evolution scale a particular species stood, the more it was dependent on oxygen content in the environment, the further it was losing the ability to survive at lowered oxygen percentage. Moreover, the survivors were those life forms that quicker and more efficiently learned to utilize oxygen. Only at the embryonic stage of development have mammals retained a relative resistance to a lowered oxygen percentages.

At rest human body uses up 250 ml of oxygen and forms up 200 ml of carbonic acid gas. Oxygen reserve in human body (1.5-2.0 l) would suffice for just 5-6 minutes' time. Blood and tissues of human body store approx. 2,0 liter of carbonic acid gas and 1 l of nitrogen. According to Levi and Zuntz lungs can provide penetration of 6080 ml of oxygen per minute into human blood, while at rest a man consumes just 250 ml, under load - 3000-4000 ml. Lungs quite cope with their task in a healthy body. Normally 100 ml of blood contain 19-21 ml of oxygen.

In nature an intensive gas exchange by animals can be effected not only through lungs. Carbonic acid gas excretion by a frog is effected through the skin and amounts approx. 85 percent, i.å. far exceeding the lungs. In case of human being the skin respiration part is 1.9 % of the taken-in oxygen and 2.7% of the excreted carbonic acid. During the intrauterine development oxygen reaches the fetus by a quite complicated chain: oxygen of the air - lung alveolae - the mother's erythrocytes - placenta - fetus's erythrocytes - fetus's organs and tissues.

According to studies, ability of mammals to stay long under water is accounted for by a number of developed physiological mechanisms - the ability to thriftily consume the available oxygen, ability of muscles and heart to endure oxygen deprivation, relatively low sensitivity of tissue to ÑÎ2 and lactic acid accumulation, blocking a large part of the circulation system (e.g. the lower part of the trunk while retaining blood supply of the brain), ability to slow down the cardiac rhythm (from 80 b.p.m. to 10 b.p.m. by a seal), to increase the efficiency of the locomotory function of muscles, to lessen the aerobic respiration activity and heighten the anaerobic metabolism intensity. Oxidation metabolism is sinking , for example, by poikilotermic animals with their acclimatizing to low temperatures and lowered oxygen percentages. Some mammals (hedgehogs) can substantially lower the metabolic processes intensity while hibernation, at that they can sustain a considerable oxygen reduction for several hours, during non-hibernation period they would soon die, though.

Experiments with eggs of sea hedgehog, with cardiac muscle of mammals and yeast have revealed that cytochrome system of the cell can sustain ÐÎ2 reduction down to 2,5 volume percent, normally this value amounts to 19 absolute percent, i.å. up to 13 percent of the regularly supplied value. This is in a way reflects a system of biological protection of tissues from accidental or otherwise oxygen content reductions in blood tiding to an organ.

Apparently, cells die in a medium of low oxygen content due to insufficient amount of generated energy needed to maintain a normal physiology and molecular structure of cells and their membranes. An increased oxygen content is also tocsic though. There is a common knowledge fact of the so-called oxygen "burn" of lungs caused by inspiring pure oxygen, or retina damage and blindness by the newborn. Chrysalis pupae of hymenopterous Habrobracon, being put for 1 hour under 1 bar of Î2 or for 5 minutes under 2 bar, reveal cytological damages and reduced metabolism at the stage of mature individuals. Several bar Î2 pressure can be tocsic to mammals; thus mice, being subject to staying for 5 hours under 6 bar pressure, die. Tocsicity can be reduced by introduction of reducing agents - glutathione and cystein, which is a sign of forming up of a large number of radicals and peroxides. Dehydrogenases of pyruvic and succinic acids and triosedehydrogenases are inhibited by a high oxygen content.

À.V. Voino-Yasnetsky (1958), having studied the toxicity effect of high pressure oxygen onto a number of representatives of Annelida, arthropoda, cyclostomata fishes, amphibia and mammals, revealed that a common regularity is a sequential blocking of phylogenetically young functional systems with simultaneous release of older systems of central nervous system, which function on the earlier phylogenesis stages. In this respect it is worthy of note that all animals have enzymes for anaerobic glycolytic metabolism. Some animals lead an anaerobic mode of life, others need a small amount of oxygen, still glycolysis remains by them the main type of metabolism, oxygen being present in the medium though. Many animals can change over to the anaerobic metabolism, though be it for a short-term period.

Considering the significance of various functions in the organisms of mammals and the man, first of all provision of cells with oxygen should be highlighted, the function that in principle limits the survival rate of aerobic organisms. In our opinion the organs that determine this function as prior must have a direct bond and a feedback from all other systems, organs, tissues and cells in order to ensure interrelation and vital activity of the organism as a whole. In other words, he prime circuit lungs - cardiovascular collector is first of all linked to the tissues, determining maintenance of rheology (including the amount) of blood and hemopoiesis, to the osteomuscular cage of lungs and to the parts of nervous system responsible for automatic character of its functioning. A second circuit includes organs and tissues to this or that extent responsible for ensuring the functioning of the prime circuit (gastroenteric tract, liver, kidneys, endocrine glands etc.). They certainly all need oxygen and each of them has a direct and back link mechanism to the prime circuit for purposes of urgent oxygen delivery, as well as for long-lasting conditions of chronic hypoxia.

From the evolution point of view the organ itself does not determine the survival rate, the resistance rate of the entire organism depends on interrelation of organs and tissues implementing a particular function or ensuring the keeping-up (homeostasis) of this or that vital parameter, at that the more ancient in the evolution sense a particular function, the more resistant it is in face of a certain negative factor of the environment (it wouldn't have survived otherwise).

On the other hand, pulmonary breathing physiology consists, as it were, of three stages - the inspiration part or the oxygenation stage proper, air being sucked into respiratory tracts; the diffusion part, or gas exchange, accompanied by a corresponding process of alveolar blood flow in this part of pulmonary tissue; and the expiration part or, relatively, the hypercapnic stage, characterized by an almost 50-100 times' carbonic acid gas content increase in the expired air. It should be mentioned that all these three mechanisms have different modes of regulation, different levels of bond to various organs and tissues of the organism.

Analysis of the literature and our own observation have revealed that respiratory exercises can have an important conditioning effect onto the cells and tissues of the entire organism, providing forming-up of a sanative effect in view of the ailment processes, heightening the body's resistance to alteration factors and increasing the vital cycle active phase duration. The prime mechanism by which this biologic phenomenon is effected is the presence of lungs activity functional bond to all the organs and systems of the organism, taking into account the importance of blood oxygen saturation of all the cells.

Considering the interaction vectors of lungs we should first of all highlight several prime groups.

1. The structural-physiological provision: à) cardiovascular system functioning (myocardium and vascular collector, osteomuscular frame (intercostal muscles, the diaphragm and nerve centers, ensuring the expiratory and inspiratory provision), b) the hemopoiesis organs, particularly erythroesis (red bone marrow and the extramedullar hemopoiesis foci), c) cutis with all its derivatives.
2. The trophic and metabolic provision: à) intestine, pancreas and liver, osteomuscular frame. b) hydrous-saline homeostasis (adrenal glands , connective tissue elements).
3. The immune protection organs and tissues (thumus, spleen and lymph knodes).
4. Neuroregulatory provision: à) endocrine organs (thyroid gland, renal gland, sexual glands, parathyroid gland etc.), b) truncal part of cerebrum (respiratory and cardiovascular muscles), hypothalamus, cerebral cortex.

The data and results gained through the research give evidence as to the presence of functional and neuroendocrine bond of lung physiology to all the systems, organs and tissues of the body, thus accounting for the sanogenetic and curative effect of aptly selected respiratory exercises.