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  • Composition and functions of blood

    BLOOD – liquid tissue, its extracellular substance – PLASMA – consists mainly of water. In plasma morphologic elements are suspended – BLOOD CELLS. The blood circulates in the VASCULAR SYSTEM, closed or open – then it is called HEMOLYMPH.

    PLASMA – liquid extracellular substance, it is a product of many cells of the body.
    It takes up 55% of mammals' blood volume. It consists of:

    • water – 92%
    • proteins – 7% - albumins, globulins,
    • fibrinogen
    • other organic compounds: glucose, amino acids, lipids
    • non-organic compounds in nature of electrolytes - they contain sodium, potassium, chlorine, calcium, magnesium, carbohydrate, phosphorus ions.

    PLASMA FUNCTIONS:


    thank to albumins and electrolytes it keeps the osmotic pressure of the body liquids and Ph-factor on the constant level
    it transports nutritious substances, oxygen, carbon dioxide, harmful products of nitric compounds metabolism, hormones
    thank to globulins it has the protective function, i.e. it protects the body from harmful compounds - ANTIGENS – macromolecular substances in nature of proteins, carbohydrates and nucleic acids: in dust, flower pollens, bacteria, viruses, mould, parasites. GLOBULINS are proteins that bind to antigens that become harmless for the body. Globulins are antibodies, they neutralize foreign bodies.
    fibrinogen, dissolved in plasma, can metamorphose into fibrin that blocks damaged blood cells, prevents from bleeding.

    BLOOD CELLS – we divide them into three groups:
  • erythrocytes – red blood cells
  • leukocytes – white blood cells
  • thrombocytes – platelets

    ERYTHROCYTES – in embryos they are produced in their GALL BLADDER, then in their LIVER, and starting from the second half of their lives – in their BONE MARROW. They are oval single-nucleus cells. Only in mammals they lose their nuclei and adopt the form of flattened circles, thinner in the centre.
    In erythrocyte cytoplasm – HAEMOGLOBIN (red) that enables transport of oxygen and carbon dioxide. In the human body there are about 4,3 million (women) and 4,8 million (men) of erythrocytes in 1 millilitre of blood.

    LEUKOCYTES – produced in RED BONE MARROW, some of them (lymphocytes) in thymus, spleen and lymph nodes. They are the most diverse cells, morphologically and functionally. In the human body: 4-10 thousand in 1 millilitre of blood.
    granulocytes – about 60%
    monocytes – about 4%
    lymphocytes – about 36%

    THROMBOCYTES – oval single-nucleus cells. They are produced in RED BONE MARROW. In 1 millilitre of the human blood there are 200 – 400 thousand of platelets. Thrombocytes start the process of blood clotting. During cracking of the blood vessels they release THROMBOKINASE – an enzyme that starts the process of transformation of fibrinogen into blood fibrin.

    Blood components that leach through blood vessels to intercellular spaces of other tissues, form LYMPH – they contain most plasma elements and white blood cells. Circulation of blood and lymph contacts indirectly particular body cells with each other – cooperation and forming of an integral whole, the so-called ORGANISM.

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