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18.1, 18.2, , 18.3, , 18.4, , 18.5, , 18.6, , Hosochis, , Blood, , Lymph (Tissue, Fluid), Circulatory, Pathways, Double, Circulation, Regulation of, Cardiac Activity, , Disorders of, Circulatory, System, , Ciarrer 18, , Bopy F LUIDS AND Circutation, , You have learnt that all living cells have to be provided with nutrients, O,, and other essential substances. Also, the waste or harmful substances, produced, have to be removed continuously for healthy functioning of, tissues. It is therefore, essential to have efficient mechanisms for the, movement of these substances to the cells and from the cells. Different, groups of animals have evolved different methods for this transport. Simple, organisms like sponges and coelenterates circulate water from their, surroundings through their body cavities to facilitate the cells to exchange, these substances. More complex organisms use special fluids within their, bodies to transport such materials. Blood is the most commonly used body, fluid by most of the higher organisms including humans for this purpose., Another body fluid, lymph, also helps in the transport of certain substances., In this chapter, you will learn about the composition and properties of, blood and lymph (tissue fluid) and the mechanism of circulation of blood, is also explained herein., , 18.1 Bioop, , Blood is a special connective tissue consisting of a fluid matrix, plasma,, and formed elements., , 18.1.1 Plasma, , Plasma is a straw coloured, viscous fluid constituting nearly 55 per cent of, the blood. 90-92 per cent of plasma is water and proteins contribute 6-8, per cent of it. Fibrinogen, globulins and albumins are the major proteins., , 2020-21
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DY FLuIDs AND C TION, , Fibrinogens are needed for clotting or coagulation of blood. Globulins, primarly are involved in defense mechanisms of the body and the albumins, help in osmotic balance. Plasma also contains small amounts of minerals, like Na‘, Ca**, Mg"*, HCO;, Cr, etc. Glucose, amino acids, lipids, etc., are, also present in the plasma as they are always in transit in the body. Factors, for coagulation or clotting of blood are also present in the plasma in an, inactive form. Plasma without the clotting factors is called serum., , 18.1.2 Formed Elements, , Erythrocytes, leucocytes and platelets are collectively called formed, elements (Figure 18.1) and they constitute nearly 45 per cent of the blood., , Erythrocytes or red blood cells (RBC) are the most abundant of all, the cells in blood. A healthy adult man has, on an average, 5 millions to, 5.5 millions of RBCs mm* of blood. RBCs are formed in the red bone, marrow in the adults. RBCs are devoid of nucleus in most of the mammals, and are biconcave in shape. They have a red coloured, iron containing, complex protein called haemoglobin, hence the colour and name of these, cells. A healthy individual has 12-16 gms of haemoglobin in every, 100 ml of blood. These molecules play a significant role in transport of, respiratory gases. RBCs have an average life span of 120 days after which, they are destroyed in the spleen (graveyard of RBCs)., , Leucocytes are also known as white blood cells (WBC) as they are, colourless due to the lack of haemoglobin. They are nucleated and are, relatively lesser in number which averages 6000-8000 mm of blood., Leucocytes are generally short lived. We have two main categories of WBCs, — granulocytes and agranulocytes. Neutrophils, eosinophils and basophils, are different types of granulocytes, while lymphocytes and monocytes, are the agranulocytes. Neutrophils are the most abundant cells (60-65, per cent) of the total WBCs and basophils are the least (0.5-1 per cent), among them. Neutrophils and monocytes (6-8 per cent) are phagocytic, cells which destroy foreign organisms entering the body. Basophils secrete, histamine, serotonin, heparin, etc., and are involved in inflammatory, reactions. Eosinophils (2-3 per cent) resist infections and are also, , 279, , , , , , , , Platelets Monocyte, , ane QS Eosinophil Neutrophil T lymphocyte, 3 f ( ‘, e «§ @©@ O©Ge@, Basophil, , B lymphocyte /, , , , Figure 18.1 Diagrammatic representation of formed elements in blood
