Tiêu đề Med-RM_Zoo_SP-1_Ch-5_Body Fluids and Circulation.pdf ✅

Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph. 011-47623456 Chapter Contents All living cells require constant supply of nutrients, O2 and other essential substances. Also, the waste or harmful substances produced, need to be removed continuously for the healthy functioning of tissues. Depending upon the medium of transportation circulatory system is divided into two categories : (a) Type I where water is the medium of transportation e.g. In sponges (water canal system), in Hydra (Gastro-vascular system) and in star fish (Ambulacral system or water vascular system). (b) Type II where blood is the medium of transportation. It is further of two types: (i) Open circulatory system : Blood flows through vessels which open into tissue spaces or membrane lined sinuses., e.g., arthropods and most molluscs. (ii) Closed circulatory system : Blood flows through heart, vessels and finely branched capillaries, without coming in direct contact with body tissues or body cavity. It was discovered by William Harvey (1628). BLOOD Blood is a specialised connective tissue consisting of a fluid matrix, plasma and a cellular portion called formed elements. The plasma constitutes approximately 55% of the blood and the formed elements account for the remaining 45%. Composition of Blood Plasma Formed elements Blood platelets Leucocytes Granulocytes Agranulocytes Neutrophils Basophils Eosinophils Monocytes Lymphocytes B-lymphocytes T-lymphocytes Erythrocytes Chapter 5 Body Fluids and Circulation Blood Lymph (Tissue Fluid) Circulatory Pathways Regulation of Cardiac Activity Electrocardiogram (ECG) Disorders of Circulatory System
148 Body Fluids and Circulation NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 Plasma Plasma is a straw coloured, viscous fluid forming matrix of the blood (matrix is the ground substance of a tissue / a non-living substance occupying the space between cells). Composition of Plasma 1. Water: 90-92% of plasma is water. 2. Proteins: They constitute about 6-8 percent of it. Fibrinogens, globulins and albumins are the major plasma proteins. (i) Fibrinogen: Fibrinogen is an important clotting factor produced by the liver. (ii) Globulins: Globulins are primarily involved in the defense mechanism of the body. They are grouped into three subtypes: alpha globulins, beta globulins, and gamma globulins. Gamma globulins are antibodies which function during immune response of the body. (iii) Albumins: Albumins help in maintaining osmotic balance. They maintain the osmotic pressure needed to draw water from the surrounding tissue fluid into the capillaries. This action is needed to sustain blood volume and pressure. 3. Minerals: Plasma contains small amounts of minerals like Na+, Ca++, Mg++, HCO3 –, Cl– etc. 4. Glucose, amino acids, lipids etc. are also present in the plasma as they are always in transit in the body. They are being carried by the plasma from one place to another. These substances enter and leave the plasma at regular intervals. Plasma without the clotting proteins is called serum. Formed Elements Table : Summary of Human Blood Corpuscles S.No. Name and Number/ Percentage Colour and Structure Formation and Life Span Function 1. Erythrocytes ( RBCs) In man and woman 5-5.5 million per cubic millimeter of blood. Number increases during exercise and at high altitudes. Appear yellow when seen singly and red when viewed in bulk, circular, biconcave, enucleated, elastic plasma membrane, homogenous cytoplasm with haemoglobin; cell organelles such as ER, mitochondria, ribosomes, centrioles are absent; 7-8 m wide, 1-2 m thick. Synthesized in yolk sac in the early few weeks of embryonic life, in later embryonic stage by the liver and spleen, from birth onwards by bone marrow. Life span is about 120 days. Older erythrocytes are removed from the circulation by phagocytic cells of spleen. Spleen is also called graveyard of RBC. Transport of oxygen and some amount of carbon dioxide. during infection. 2. Leucocytes (WBCs) 6000-8000 per cubic millimeter of blood. Number increases Colourless, rounded or irregular, nucleated, 12 to 20 m wide. Bone marrow, lymph nodes, spleen, thymus, tonsils and Peyer's patches. Act as soldiers, scavengers, some help in healing. (i) Agranulocytes Cytoplasm lacks granules, nucleus not lobed. (a) Lymphocytes 20-25% Large rounded nucleus, scant cytoplasm. Lymph nodes, spleen, thymus, tonsils, bone marrow, Peyer's patches. Life span is about few days or months or even years. Motile non- phagocytic, secrete antibodies, help in healing.
NEET Body Fluids and Circulation 149 Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 (b) Monocytes 2-10% Largest of all types of leucocytes. Nucleus bean shaped, enough cytoplasm. Bone marrow, Life span is about 10 to 20 hours. Motile, phagocytic, engulf germs and cell debris, often change into macrophages. (ii) Granulocytes Cytoplasm has granules, nucleus lobed. (a) Eosinophils 2-3% Bilobed nucleus, coarse granules in cytoplasm, take acidic stain. Bone marrow, life span is about 4 to 8 hours in the blood 4 to 5 days in the tissue. Increase in number during allergy, play role in immunity. (b) Basophils 0-1% (Least in number) Usually three lobed nucleus, less number basic stain. Bone marrow, life span is about 4 to 8 hours in the blood. Release heparin and histamine. Thus, they act like mast cells of connective tissue. (c) Neutrophils 60-65% (Most abundant) Many lobed nucleus, fine granules; take acidic as well as basic stains. Bone marrow, life span is about 4 to 8 hours in the blood, 4 to 5 days in the tissue. Phagocytic; engulf germs and dead cells. 3. Platelets 1,50,000-3,50,000 platelets per cubic millimetre of blood. Colourless, rounded or oval, non-nucleated fragments of the cells. Bone marrow, life span is about a week. Help in blood clotting. S.No. Name and Number/ Percentage Colour and Structure Formation and Life Span Function RBC Platelets Eosinophil Basophil Neutrophil Monocyte T-lymphocyte B-lymphocyte Fig. : Diagrammatic representation of formed elements in blood Blood Groups There are certain molecules on the surfaces of all cells in the body that can be recognized as foreign by the immune system of another individual and hence can induce the immune system of latter. These molecules are known as antigens. As part of the immune response, particular lymphocytes, secrete a class of proteins called antibodies that bind in a specific fashion with antigens. The membranes of red blood cells (RBCs) also possess several antigens. Depending on the nature of antigens present on the membrane of RBCs, various types of blood grouping have been done. Two such groupings- the ABO and Rh – are widely used all over the world. ABO grouping Karl Landsteiner (1901) along with his coworker recognised four types of blood groups in human beings, commonly known as ABO blood grouping. ABO grouping is based on the presence or absence of two surface antigens on the RBCs namely A and B. Similarly, the plasma of different individuals also contain two natural antibodies called anti-A and anti-B. Transfusion Reactions In many clinical conditions blood transfusion is needed. In such cases the donor’s blood and recipient’s blood must be compatible to avoid severe problems of clumping (destruction of RBC).
150 Body Fluids and Circulation NEET Aakash Educational Services Limited - Regd. Office : Aakash Tower, 8, Pusa Road, New Delhi-110005 Ph.011-47623456 A major cross-match is made by mixing serum from the recipient with blood cells from the donor. If the blood groups do not match, for example, if the donor’s blood group is ‘A’ and the recipient’s blood group is ‘B’, the recipient’s antibodies attach to the donor’s red blood cells and cause clumping (agglutination). Transfusion errors that result in such agglutination can lead to blockage of small blood vessels and cause hemolysis (rupture of red blood cells). Therefore, the blood of a donor has to be carefully matched with the blood of recipient before any blood transfusion. The donor’s compatibility is shown below: Blood group Antigens on RBCs Antibodies in plasma Donor’s group A A anti-B A, O B B anti-A B, O AB A, B nil AB, A, B, O O nil anti-A, B O From the above mentioned table it is evident that blood group ‘O’ can be donated to persons with any other blood group and hence ‘O’ group individuals are called ‘universal donors’. Group ‘O’ red blood cells lack A and B antigens, therefore the recipient’s antibodies cannot cause agglutination of the donor’s RBCs. Persons with ‘AB’ group can accept blood from persons with AB as well as the other groups of blood. This is because blood group AB lacks anti-A and anti-B antibodies and thus cannot agglutinate donor’s red blood cells. Therefore, such persons are called ‘universal recipients’. Rh Grouping Another group of antigens found on the red blood cells of most people is the Rh factor (Rh stands for rhesus monkey, in which these antigens were first discovered). It was discovered by Landsteiner and Wiener. People who have these antigens are said to be Rh+ve, whereas those who do not are called Rh–ve. An Rh–ve person, if exposed to Rh+ve blood, will form specific antibodies against the Rh antigen. Therefore, Rh group should also be matched before transfusions. A special case of Rh incompatibility (mismatching) has been observed between the Rh–ve blood of a pregnant mother with Rh+ve blood of the foetus. The Rh–ve mother is not usually exposed to the Rh antigen of the foetus during the first pregnancy as the foetal and maternal blood are normally kept well separated by the placental barriers. However, at the time of birth of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh+ve blood from the foetus. In such cases, the mother starts preparing antibodies against Rh antigen in her blood. These antibodies could cross the placental barriers in subsequent pregnancies and cause hemolysis of the Rh+ve red blood cells of the foetus. This could be fatal to the foetus or could cause severe anaemia and jaundice to the baby (HDN - haemolytic disease of newly born). This condition is called erythroblastosis foetalis. Erythroblastosis foetalis can be prevented by injecting the Rh–ve mother with an antibody preparation (anti-Rh antibodies) against the Rh factor immediately after the birth of each Rh+ve baby. Coagulation of Blood When you cut your finger or hurt yourself, the wound does not continue to bleed for a long time. It usually stops bleeding after sometime as blood exhibits coagulation or clotting in response to an injury or trauma. This is a mechanism to prevent excessive loss of blood from the body. A dark reddish brown scum is formed at the site of a cut or an injury over a period of time. It is a clot or coagulam formed mainly of a network of threads called fibrins in which dead and damaged formed elements of blood are trapped. Mechanism of Blood Coagulation Blood clotting is achieved in several steps : (i) Blood platelets disintegrate on coming in contact with air and release platelet factor-III or platelet thromboplastin.