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CELL THEORY

All living organisms, with the exception of viruses, are made up of cells. Cells, most often represented by microscopic formations, have all the most important vital properties: self-regulation, self-reproduction, unity of structure and function, historical development, etc. The cells constantly undergo metabolic processes and energy conversion.

The science that studies the structure and functioning of cells is called cytology (from the Greek. Kytos - cell + logos - science). The development and formation of cytology was largely determined by the improvement of the microscopic technique, since cells are difficult to study with the naked eye.

In 1665, the English natural scientist R. Hooke first reported the existence of cells. He examined under a microscope improved by him thin sections of the cork and found small empty pores and cells, which he called cells. Strictly speaking, R. Hook observed dead cells in the cork section, deprived of living contents that filled them. Exploring under a microscope various parts of other plants, in particular carrots, burdock, fern, he found the same structure plan as that of cork.

In 1677, M. Malpighi reported on the cellular structure of all the plants he studied. Prominent scientist of the 17th century A. van Leeuwenhuk, examining a drop of water under a microscope, discovered the simplest single-cell organisms. For a long time, the cell's main structural component was recognized as its membrane.

After the beginning of the XIX century. there was a technical improvement in the quality of the lenses, quickly increased attention to research using a microscope. In 1825, Czech scientist J. Purkinje showed that inside the cell there is a gelatinous substance, later called cytoplasm. English botanist R. Brown described the cell nucleus. The German botanist M. Schleiden in 1837 concluded that all plant cells contain nuclei.

In 1839, the German zoologist T. Schwann, summarizing his own experimental data and the results of other scientists, formulated a concept currently known as cell theory. According to cell theory: 1) the cell is the main element of life; 2) any organisms consist of one or many cells. Indeed, despite the enormous diversity of living beings, differing in size (see table), shape, habitat, method of movement, energy supply, etc., the basis of their morphofunctional organization are cells. R. Virkhov in 1855 added to these two postulates a fundamental position: “Omnis cellula e cellulae” - “Every cell from a cell”. In other words, the third position of the cell theory states that all cells are formed only as a result of the division of other cells.
The current content of cell theory can be summarized as follows: the main structural and functional unit of living organisms is the cell.

Cellular theory is the most important achievement of natural science. She played a prominent role in the development of not only biology and medicine, but also many other branches of the science of man.

The subsequent successes of cytology and cytogenetics were associated with the development and improvement of research methods. The central role of the nucleus in cell division was proved after the invention of the method of staining cytological preparations by V. Fleming in 1879. The development of light microscopes made it possible to obtain new information about the structure of the cell and some of its structures. However, the resolution of the light microscope is limited by the ability of the human eye, which can perceive two points separately at a distance of not less than 0.1 mm. With this resolution, some cellular structures are not visible, and the study of others is significantly more difficult.

A major step forward was an invention in the 30s. electron microscope V. Zvorykin and phase contrast microscope F. Zernike. An increase of 100 thousand times, which provides an electron microscope, allows you to study the smallest details of cellular organelles. Modern advances in cytology and cytogenetics are associated with the development of chemical, physical methods and technologies (from X-ray analysis to computer databases).

In multicellular organisms, each cell is specialized to perform, as a rule, one of the functions necessary to ensure the vital activity of the organism as a whole.

Depending on the function they perform, cells can vary significantly in terms of size, shape, location in various tissues and organs of the body, as well as other external and internal characteristics.

We indicate the main types of specialization of cells of a multicellular organism. It:

? perception of external and internal stimuli;

? coordination of all functions (cells of the nervous and endocrine systems);

? movement and support;

? protection of the body (cells of the epithelial tissue and the immune system);

? obtaining nutrients or their synthesis;

? transfer of nutrients, biologically active substances, gases, etc .;

? removal of decay products; reproduction.
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CELL THEORY

  1. CELL THEORY
    As a result of a huge number of microscopic studies in the XVII — XVIII centuries. accumulated a wealth of factual material about the structure of plant and animal organisms. However, the metaphysical way of thinking inherent in feudalism that prevailed at that time did not contribute to the theoretical generalizations of these facts. Considering nature as an accidental accumulation of objects created
  2. Cell cycle Cell cycle regulating molecules open the door to diagnosing and killing cancer cells
    In the body of an adult there are 5 • 1013 (VN Soyfer, 1998) or 5 • 1014 (V. Tarantula, 2003) cells. Each cell of any type is a part of its tissue and the body as a whole. A cancer cell in a human body is no longer a part of the tissue and its organism, but an independent cell that has separated from them. This is a cell-organism. Cell division is the main property and a sign that it
  3. What is the difference between sickle cell anemia and sickle cell anomaly?
    In cases where a genetic defect in adult hemoglobin is present on both the maternal and paternal chromosomes (No. 11), the patient is HbS homozygous and suffers from sickle cell anemia (HbSS genotype). When a defective gene is present on only one chromosome, the patient is heterozygous for HbS and suffers from a sickle cell abnormality (HbAS genotype). When a sickle cell anomaly is formed
  4. Hepatocellular failure
    Despite significant compensatory abilities of the liver and its high regenerative activity, massive necrosis or severe hepatocyte dystrophy lead to the development of hepatocellular failure syndrome, accompanied by dysfunction of various organs and systems. Acute hepatocellular insufficiency may develop with fulminant (acute) course of acute
  5. Cell respiration
    The main function of the lungs is to provide gas exchange between venous blood and inhaled air. The need for gas exchange is due to the aerobic nature of cellular metabolism, which requires the continuous flow of oxygen into the body and the excretion of carbon dioxide.
  6. Sickle Cell Hemoglobinopathies
    Widely distributed among the inhabitants of tropical Africa and in some regions of India, are less common in the countries of the Mediterranean, the Near and Middle East, in America. In connection with the widespread migration of the population, they recently began to meet in Western Europe. The main defect in this pathology is the production of IBB as a result of spontaneous mutation and deletion of the P-globin gene by
  7. CELL MEMBRANE
    The cell is surrounded by a semipermeable membrane. It is called semi-permeable, because some substances can pass through it freely, while others cannot pass at all. The first generalization we can make concerns that small molecules such as water or oxygen can pass through the cell membrane freely, while large molecules like starch or protein cannot. The most
  8. Cellular basis of immune response.
    A specific immune response is provided by lymphocytes. Antibodies are produced by B-lymphocytes, and cellular immune responses are realized by T-lymphocytes. These lymphocytes are often referred to as B and T cells. Lymphocytes develop in the bone marrow from a common precursor cell. Further, differentiation (maturation) occurs either in the tissue of the bone marrow (B cells) or in the thymus (T cells). These
  9. Case study: a patient with sickle cell anemia
    A 24-year-old black woman, who had a history of hereditary sickle cell anemia, was admitted to the clinic with complaints of abdominal pain, and she is planned to undergo cholecystomy. The patient believes that she suffers from sickle cell
  10. Basics of cell cycle regulation
    Blood - exists in the form of a liquid component and solid formations. Its liquid part - the blood itself - consists of cellular and non-cellular divisions. The solid part is represented by blood-forming organs, which determine its cellular composition (bone marrow, lymph nodes, thymus gland), foci of aggregation of formed elements in other places (Peyer's intestinal plaques, etc.) and organ, where
  11. Cell mediated immunity.
    Various effector functions attributable to cell-mediated immunity are subject to T-cells, which play a central role in the regulation of a specific immune response and provide stimulation of many nonspecific inflammatory mechanisms. T-cells account for about 70% of peripheral blood lymphocytes. There are two main groups of effector T cells: cytotoxic T lymphocytes
  12. Topic: Cellular Immunity
    Lymphocyte subpopulations. Determination of subpopulations of T- and B-lymphocytes: cluster analysis, E- and EAC-rosetting, evaluation of the functional activity of immune cells, blast transformation of blood lymphocytes into mitogens, alloantigens, determination of the activity of NK cells. Detection methods: lymphocyte blast transformation reaction, lymphokine production, macrophage and leukocyte migration inhibition reaction,
  13. Sickle cell anemia (HbS).
    A form of hemoglobinosis, a characteristic feature of which is the presence of a mutant autosomal gene, leading to the replacement of valine with glutamic acid in the sixth position of the globin beta chain. This type of anemia is widespread among the population of tropical Africa and in some regions of India, less common in the countries of the Mediterranean, the Middle East, Georgia, Azerbaijan, America. AT
  14. Cellular and humoral immunity indicators
    Cellular and humoral indicators of immunity - characteristics of cells and substances of the internal environment, reflecting the immune activity. Indicators of the readiness of cells and body tissues to detect and bind foreign molecules are the amount of antibodies and other molecules involved in immune reactions, as well as the degree of activity of the labels of tissues and body fluids.
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