TYPES OF DAMAGE ON DIFFERENT LEVELS OF multicellular organisms

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Damage - violation of biological structure, leading to disruption of the structure features resulting from interaction with the damaging factor. Damage - the initial link in the pathogenesis (development mechanism) of disease; Pathogenic factors can cause damage by acting directly on the biological structure of the organism (primary) and indirectly - as a result of the launch of responses, many of which are themselves capable of causing an additional, secondary damage.

The action of various pathogenic factors can lead to damage at various levels of organization of life: molecular, subcellular, cellular, tissue, organ, system and organism. The interaction of structures of any of the above levels capable entail either reversible, able to be restored, or irreversible, not able to heal the injury.

Two main types of damage can be distinguished at the molecular and subcellular levels:

- A destruction - irreversible destruction of biomolecules to their components or simple inorganic substances

- Modification - reversible change in the structure of protein molecules without destroying them.

For example, non-specific toxic chemicals (strong oxidizers acid. Alkalis, etc.), high doses of ionizing radiation, high temperature, causing coagulation of protein, lead to the destruction of all living structures irreversibly destroying components of biomolecule. On the contrary, "a modification of a protein receptor molecule to molecule acetylcholine muscle relaxant ditilina leads to its reversible change, making it impossible to the normal response of the receptor to acetylcholine. Although this structure does not fracture the receptor occurs, resulting in impaired transmission of electrical pulse at the neuromuscular synapse, resulting in paralysis of muscles, including respiratory. As a result, the body can die from lack of oxygen due to reversible changes in the structure of only one of the proteins. Thus, there are specifically toxic chemicals, including many drugs and poisons.

Thus, damage (alteration) - a comprehensive term, it includes the destruction - destruction, and any change in the biological structure at all, violating its function.

Damage at the cellular level. Cage - an elementary biological system capable of self-renewal, self-reproduction and development. Interaction between cells and the external environment is a necessary condition for maintaining the operating life of the organism. In this cell, although subject to the general correlative influences and links from other cells and the organism as a whole, but also works by its own laws and in Rada cases may go out of control these common correlative influences.

Normal cells respond to the constantly changing demands and external influences. The cell is capable of changing the structure and function in a fairly narrow range. If it is excessive impact or are pathological factors, it can be adapted, reaching a steady state, in order to maintain adequate cell activity in the changed circumstances. If the cell can not be adapted or adaptable possibilities have been exhausted, there is damage that is reversible to a certain point, but if the effect of excessive or prolonged, irreversible changes and the cell is doomed.

The term equivalent death as irreversible damage we may apply to biological structures, since their level of cellular organization. Irreversible damage at the cellular level have her death, which can be violent (murder) - necrosis and non-violent (suicide) - apoptosis.

You can draw an analogy with the free-standing tree in the wind: it bends and sways to a certain point, but quickly regains its original position when a gust of wind ceases. The stronger the wind can blow the leaves and broken branches, but the damage is not fatal, the hurricane can also pull out a tree by the roots, resulting in irreversible damage, in which survival is impossible,

It involves whether for a specific effect of adaptation or damage (reversible or irreversible), depends not only on the nature and intensity of the current factor, but also from the many conditions that occur in these cells and their microenvironment, such as the degree of differentiation that preceded the impact of the state of the cell, blood supply, supply of nutrients, and you can find the following general rule: the faster the cells divide and the more oxygen consumed (ie, the higher the intensity of metabolism in the cells), the more they are susceptible to damage by the action of various factors and changing conditions of existence. The validity of this statement we can still repeatedly seen by considering hypoxic, and other types of radiation damage to the cells of various organs and tissues.

The problem of studying the sequence of events when damaged cells at the molecular level is rather complicated. Cell damage can be caused by various reasons, and will likely have a specific pathway leading to cell death. Many macromolecules, enzymes, organelles inside the cell interact so closely that it is impossible to identify a primary object damage. The boundary separating the reversible and irreversible changes, and has not yet been determined.

However, there are certain structures and processes, it is absolutely necessary for the life of the cell, the violation of which leads to her death:

- The integrity of the cell membrane structure and its receptor system, which is necessary for the normal processes of cell metabolism and cell interaction with the environment;

- Oxidative phosphorylation and ATP production, taking place in the mitochondria, and necessary for the implementation of energy-dependent functions;

- The synthesis of enzyme and structural protein;

- The integrity of the genetic apparatus of the cell.

Let's try to systematize the factors that can disrupt the normal life of a multicellular organism cells. Violation of cell activity may be the result of:

1) deficit that it needs to produce energy in the form of ATP, an update of its own structures and maintaining internal homeostasis:

- Oxygen;

- For the oxidation of substrates (primarily glucose) structural elements (amino acids, fatty acids, etc.), And vitamins;

2) destruction in nonbiological action of high energy factors causing any degradation of the cells:

- Physical (high temperature and low temperature, ionizing radiation, electrical current, etc.);

- Mechanical;

- Chemicals - non-specific toxic substances;

3) cell specific disorders structure hormone receptors and neurotransmitters, ion channels, due to intracellular enzymes joining them specifically toxic chemical and biological toxins;

4) the immunological destruction of antibody labeled cells, such as proteins of the complement system, or phagocytes.

Separately, it should be said about the micro-organisms as a factor that damage cells. It is known that about 90% of all clinical entities caused by microorganisms. Many micro-organisms do not cause harm to a multicellular organism cells that live on the surface of the mucous membranes and skin, and even benefit, not allowing to multiply pathogenic microbes. Some of the pathogens of infectious agents (viruses, intracellular bacteria) are able to enter cells, replicate them and immediately destroy. Other penetrating into the tissue or populating mucous membranes and skin, causing damage to the tissue level (extracellular bacteria, fungi, protozoa, helminths). At the same time they use the body as a medium for their habitat, often with their pathogenicity factors (enzymes, toxins, metabolic products) destroying cells and extracellular matrix. These toxins may exhibit specific toxicity by binding to specific receptor or enzyme proteins or cellular organelles and disrupting their activities.

For example, diphtheria toxin binds to a ribosomal subunit and gives thus broadcast - beam synthesis based on the messenger RNA.

The process of introducing infectious agents in the macro-organism (colonization), highlight their pathogenicity factors, dissemination of Macro-Organism effects on the host and transfer to another macroorganism is called infection and is one of the standard forms of pathology. More, this phenomenon is seen in the course of microbiology.

Damage to the tissue level. In most cases, the introduction of infectious agents causing damage to a group of cells - tissue site. Similarly, the effect of damaging factors with high energy (mechanical trauma, high and low temperature, non-specific toxic chemicals), as well as the acute shortage of oxygen supply of cells can lead to irreversible damage to many local cells in the tissue site, their violent death - necrosis. It is usually accompanied by the introduction of infectious agents and produces stereotypical response of the body - a typical pathological process at the tissue level: inflammation. During his leukocytes and plasma proteins exit the blood vessels in the tissue for phagocytosis of dead cells and infectious agents infiltrated. Later in the place of necrosis formed coarse-fibered connective tissue - shaped scar.

Damage at the organism level. Irreversible damage to the organism level is determined by the possibility of restoring the vital functions. With regard to human (social and philosophical aspects) death is the loss of higher cognitive (cognitive, mental) functions depending on the cerebral cortex. Therefore, irreversible damage to the organism level in relation to the person is the death of the cerebral cortex, which is proved by the data of electroencephalography, magnetic resonance imaging, and others.

In all cells of our body, particularly the brain cells are critically dependent on the ATP content, which is determined by the delivery of oxygen through the blood. For this reason, it is the oxygen deficiency is the most common factor causing violation of the functioning of cells and reversible and irreversible damage.

It is an acute shortage of oxygen protects the cells most vulnerable vital organs (brain and heart) complex non-specific adaptation reactions called stress. It aims to mobilize all the functional resources of the body, blood flow redistribution and metabolic resources to the brain and heart.