Disease is a disruption of the normal functioning of the body that arise under the action of harmful factors. The disease can also be caused by defects or genetic defects.
In the appearance of hereditary diseases are also leading to changes in genetic information under the influence of external factors.
Any emergency stimulus, on the one hand, has a damaging effect on various systems and organs and, on the other hand, causes the body protective and adaptive reactions. Therefore, the disease is characterized by a combination of two interconnected processes of damage and protection.
For example in inflammatory diseases of an edema and hyperemia (a consequence of the intensified flow of blood to the inflammation) increase the resistance of the pathogenic factor due to the action in the blood phagocytes and antibodies. But often adaptive reactions of the organism in the course of the disease by themselves be damaging, pathological. So, vomiting and diarrheathat play a role in removing harmful substances from the stomach and intestines can cause severe dehydration of the body, such as cholera. That is, in the course of the disease of the phenomenon of corruption and adaptive reactions, which under certain conditions can provide recovery, intertwined (see Pathogenesis).
When illness conventionally, there are organic disorders when there are persistent changes in the structure of the affected organ, and functional when prevail phenomenon of dysfunction, and cause them to structural changes are small and are reversible.
Each disease is the suffering of the entire organism, although for a number of diseases is most marked the defeat of one or a group of bodies. For example, typhoid fever is common infectious disease of the body with primary localization of changes in the small intestine. Even strictly local changes essentially serve as a manifestation of certain violations of certain processes in the body. So, stomach ulcers - only local manifestation of common diseases peptic ulcer disease. And Vice versa: any local pathological process (trauma, suppurative focus) in one way or another suffers and the organism as a whole. Therefore, as a rule, in the treatment of so-called local diseases, in addition to local, appoint and General therapy.
The causes of the disease varied (see Etiology), and many of them, causing the disease from one person to the other, do not cause noticeable violations. In addition, considering the disease as certain deviation from normal life, we should remember that the concept of "normal" extremely variabelno and depends on many factors: geographical, social, age, gender, and on the reactivity of the organism (see). If pathogenic factor and caused the disease, it flows not every patient equally, depending on the specifics of his body and the environment. Therefore, the treatment of the disease are guided by the principle "do not cure the disease and the patient."
The combination of all available manifestations of the disease makes it possible to establish its presence and to determine the nature (see Diagnosis). In the course of the disease distinguish several periods. Usually from exposure to pathogenic factor to the onset of clinical signs is held one time or another - latent (incubation in infectious diseases) in the period. It may range from moments (for example, in case of injury) to several years (leprosy). Detection of the disease in this period is of great importance for the prevention of the spread of the disease (isolation of the patient), and in some cases (for example, when the rabies, tetanus) for medical interventions, effective only during this period. An important feature is acute radiation sickness (see), in which before the latent period immediately following the action of penetrating radiation (external exposure) there is a short phase of the primary reaction with a number of pathological manifestations.
Following the latent period is called the prodromal. It is characterized by the growth of clinical symptoms from their first manifestations to full development, when the third period - the period of the disease.
Downstream there are acute and chronic diseases, with honors from chronic diseases acute is not only the duration of the course, but in some cases, the alternation of the periods of exacerbation and attenuation diseases (such as tuberculosis, rheumatism). Sometimes chronic illness has a constantly progressive course.
For some diseases (erysipelas, dysentery) is characterized by relapses, that is, flash after apparent recovery (see Relapse). In some cases, symptoms may appear vague - so-called erased form a disease can flow easily and its symptoms disappear, sometimes not having reached full development,the so - called abortive form.
Typical disease can sometimes change affiliate complication, that is a pathological process that is not due to the very cause of the disease, and additional factors, arisen in the course of the disease (for example embolism when thrombophlebitis limbs, thrombosis sinuses meninges when the carbuncle faces etc). Complications of diseases should be distinguished from intercurrent diseases not related to the disease nor etiological or pathogenically (for example, hospital-acquired infection with measles and others; see Nosocomial infections), as well as from the consequences of the disease (for example, valvular disease with rheumatic heart disease).
The final period of the Exodus, the disease can go either suddenly breaking off (crisis), or gradually (lysis). The outcome of the illness can be a full recovery, a partial recovery, the development of stable pathological changes in the body or system, and death. With full recovery all the symptoms disappear. After many infectious diseases remains the immune system (see)- immunity to infection. Sometimes the functions of the body mainly normalized, but in a separate bodies can be certain so-called residual effects expressed in infringement of function or structure of these bodies (incomplete or partial recovery). May develop persistent changes in the organ or system, giving rise to new illnesses (such as heart disease as the result of endocarditis).

The disease is violation of vital activity of organism, arising in response to extreme stressors external and internal environment. The violation of vital activity under the conditions of the disease may manifest itself as inadequate and the disorganization of the functions of various organs and physiological systems of the body, and a small, limited functional changes, sometimes subtle modern research methods. Changes of currency and structures that are the basis of any violation of the functions and, consequently, any disease that can also be expressed in different ways: for example, in the form of a deep disruption of processes of energy or protein synthesis with the phenomena of necrosis, or, on the contrary, in the form of thin changes of energy and plastic currency, accompanied by the most minor morphological cyto - and histochemical or immunochemical changes. Factors that could cause damage to the body, the violation of its functions and the development of the disease, are extremely diverse (see Etiology). Some manifestations B. may be due to hereditary or fetal effects. In the process B. damage and dysfunction very soon lead to the mobilization of adaptive resources of the organism. Unfolding this reaction limit the spread of damaging factors, sometimes provide for their destruction and reconstruction of the destroyed structures and functional compensation of damage due to the intensive activity intact organs and systems. Thus, in the course of the disease of the phenomenon of corruption and adaptive reactions of the organism, which under certain conditions can provide recovery, intertwined (see Pathogenesis).
Observed in conditions B. response of the organism are not qualitatively new, appeared together with the emergence and development of the disease; rather, they represent the adaptive response of healthy organism under the influence of extreme factors that caused the damage to the body, changed its intensity, duration, spatial distribution. In conditions B. these reactions are not always maintain their adaptive, useful for the organism is. Often there is a transformation of adaptive reactions of the organism in the pathological, the simultaneous presence of I. P. Pavlov considered characteristic of the disease. One of many examples of this kind of transformation is the development of edema and ascites in case of insufficiency of the heart. It is shown that in the occurrence of these phenomena, in some cases, plays an important role due to the primary hemodynamic and salt exchange hypersecretion renin juxtaglomerular apparatus of kidneys. Renin, in turn, is causing hypersecretion of aldosterone glomerular area adrenal cortex; aldosterone blocks all the way allocation of hydrophilic ion sodium from the body; after a delay of water and salts develop ascites and swelling. In a healthy body is the same renin-aldosterone mechanism mobilized with insufficient intake of sodium and water, for example when water-salt fasting in the desert. In these cases, the mobilization of the renin-aldosterone mechanism leads not to the development of edemas and ascites, and ensures economical use of sodium and water, i.e., perfect adaptation of the organism to the conditions of external environment.
An important manifestation of disease is violation of patient interaction of the organism with the environment, loss of the capacity to adapt to the external environment with that perfection, which is inherent in the health status (OK). Establishing B. any deviation from the norm, it should be considered that the idea of the norm must be associated with specific conditions of existence of the body. For example, in an adult normal heart rhythm alone one, but with significant physical exertion or stay at high altitude in the mountains is different. Normal blood pressure, the child is considerably lower than that of an adult, and the main exchange, on the contrary,is higher. This means that the deviation from the norm should be used to assess the development of disease-specific environmental conditions, physiological state of the organism, the stage of its ontogenetic development and mn. other
Experience the discomfort or pain (which is the word of the disease itself cannot serve as the sole criterion b, as in some periods B. they are missing, and sometimes the disease is characterized by a loss of sensitivity to pain or euphoria. When studying B. in the clinic existing methods primarily out of its manifestation, i.e. the symptoms are the point of departure for the diagnosis (see Diagnosis, Semiotics). Along with specific for a given disease pathogenesis shifts and there are common symptoms for a number B. changes and symptoms (fever, inflammation, weight loss, lack of exercise and other). These common to many B. developments have, however, when each of the specific disease specific features, specificity, which may help in diagnosis.
In occurrence and prevention B. the important role played by social factors that determine the conditions of life of society as a whole and each person individually. In this regard, it is clear that observed in our country, reducing the incidence of many diseases depends not only on the improvement of the system of the Soviet health and successes of medicine and allied Sciences, but also from comprehensive improvement of the living conditions of the population. The social value of b is that it and its effects may decrease or violate human performance. To limit the negative impact of disease on society along with the improvement of the living conditions of the population, prevention of diseases and free treatment to the importance of providing those in need, timely rest, creating for them the conditions lightweight labour by reducing the working day, change of profession, etc.
During B. distinguish the following periods: hidden or latent (incubation), prodromal, the disease development, recovery and remote consequences B. Latent period is the time between the onset of the pathogenic stimulus and the first signs B. the Definition of this period is of great practical importance for the implementation of preventive measures (e.g. disease rabies) and early treatment. Before the beginning of the latent period may be the primary reaction of the body caused by direct action of some pathogenic factors and sometimes lasted for several hours. Usually they can only be observed in the experiment, as the doctor the patients in this condition are rare. Initial reactions are largely dependent on the changes of the nervous system and, obviously, have adaptive value. Prodromal period from the appearance of the first signs of the disease to its full development; often in this period manifestations B. not typical and the symptoms are not clear. The development period is characterized by a maximum manifestations B.; however, there may be erased forms that are not accompanied by clear signs. The duration and intensity of the flow, this period may be acute or chronic; in the latter case, the disease is sluggish and lasts for months and years. B. main can be accompanied by complications (pneumonia, pressure ulcers, and others).
The recovery period, or convalescence, can proceed quickly (see the Crisis) or gradually. Recovery may be complete or incomplete, with residual effects in the form of persistent changes in various organs (see Disability). Sometimes there comes a return of the disease (see Relapse). The occurrence of relapses is not always connected with the repeated action of the reasons that caused B.; they can develop by type of trace reactions from other non-specific stimulus (the so-called second shot). Long-term effects. Sometimes after the illness and perceived full recovery after a long while developing various pathological processes that generate new clinical picture B. as pneumosclerosis, jade, cataract, leukemia and so on, These consequences of the disease, with a peculiar, "new" clinical picture, however pathogenetically associated with previously transferred diseases, such as radiation sickness. Under the action of ionizing radiation long-term effects can be detected even in later generations (see Hereditary diseases).
The clinical outcome. If the disease is not completed a full or partial recovery, it can cause permanent state of biological death, which often precede terminal States. Terminal state can be reversible and influenced various medical activities (see the Revival of the body).