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102 BODY FLUIDS AND CIRCULATION SCAN CODE Body Fluids and Circulation BODY FLUIDS AND CIRCULATION 18
BODY FLUIDS AND CIRCULATION 103 SCAN CODE Body Fluids and Circulation Chapter 18 Body Fluids and Circulation 1. Circulation-Types and Significance  Circulatory system is concerned with the circulation of body fluids to distribute various substances to various body parts.  It transports various substances such as nutrients, waste products, respiratory gases, metabolic intermediates (such as lactic acid from muscle to liver), vitamins and hormones etc.  Another function of the circulatory system is regulation of pH by means of buffer, body temperature homeostasis and water balance etc.  It plays a role in prevention of diseases by means of antibodies and antitoxins.  Different group of animals have evolved different methods for the transport such as  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. These special fluids include blood and lymph.  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. 2. Blood  Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements. It is the softest tissue in the blood and lacks fibres.  Blood is slightly alkaline with a pH of 7.4.  The pH of blood in the arteries is greater than that of the veins as the venous blood contains dissolved CO2, lactic acid and other metabolic waste that makes the venous blood more acidic.  The volume of blood in an adult of 70 kg is 5.5 litres.
104 BODY FLUIDS AND CIRCULATION SCAN CODE Body Fluids and Circulation  Plasma is a straw coloured, viscous fluid constituting nearly 55 per cent of the blood.
BODY FLUIDS AND CIRCULATION 105 SCAN CODE Body Fluids and Circulation  Plasma without clotting factor is called serum.  The composition of plasma is as follows Water: 90-92% of plasma is water Proteins: 6-8% of plasma is proteins.  Globulins: Globulins are used in defense mechanisms of the body.  Albumins: Albumin functions primarily as a carrier protein for steroids, fatty acids, and thyroid hormones in the blood and plays a major role in stabilizing extracellular fluid volume by contributing to oncotic pressure (known also as colloid osmotic pressure) of plasma. It is the most abundant blood protein in mammals  Fibrinogen: Fibrinogens are needed for clotting or coagulation of blood and are produced in the liver. During tissue and vascular injury, it is converted enzymatically by thrombin to fibrin and then to a fibrin-based blood clot.  Heparin: Heparin is a glycoprotein that acts as a natural anticoagulant preventing the clotting of blood inside the body. Specifically it is also used in the treatment of heart attacks and unstable angina Others: 2-4% of plasma  Minerals: Plasma also contains small amounts of minerals like Na+ , Ca++, Mg++, HCO3–, Cl– , etc.  Nutrients: Glucose, amino acids, lipids, etc., are present in the plasma.  Gases: Water of plasma contains dissolved gases like O2, CO2 and N2.  Excretory Products: Plasma contains excretory products like NH3 and urea. 2.2 Formed Elements Fig.18.1 Formed elements present in blood Erythrocytes, leucocytes and platelets are collectively called formed elements and they constitute nearly 45 percent of the blood. 2.2.1 Erythrocytes Fig.18.2 Structure of Erythrocyte Erythrocytes or red blood cells (RBC) are the most abundant of all the cells in blood.  An average man has 5 million to 5.5 million of RBCs mm–3of blood.  In most mammals, RBCs are enucleated and biconcave in shape. In humans, when the RBCs are developing in the red bone marrow, they do have nuclei. However, these nuclei are ejected from the cells when they enter the bloodstream in a process known as enucleation. However, in camels and llamas they are oval and without nucleus. In camels, the phenomenon of enucleation does not take place hence they have nucleated erythrocytes. In camels, erythrocytes are oval because the oval shape of the cell can circulate through thick blood and expand during dehydration. Hence in camels, erythrocytes are oval and nucleated.