Blood and its Components and cross matching

Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including: transporting oxygen and nutrients to the lungs and tissues.

1. B lood Bhavya N Kelavadiya N ursing Tutor

2. I ntroduction Blood is a connective tissue that plays a vital role to carry various life processes and protects the body against diseases. Haematology is the branch of medical science concerned with study of blood, blood-forming tissues, and blood disorders.

3. Composition of blood Blood is a connective tissue, having a liquid matrix with cells and cell fragments. Around 8% of total body weight is blood. More than half of the total blood volume is plasma and less than half is formed element: Blood plasma , a clear extracellular fluid and Formed element , composed of blood cells and platelets.

4. Functions of blood T ransportation : It transports the O2 from lungs to body tissues and carbon dioxide from the cells to the lungs. It transports nutrients from alimentary tract to the tissues. It transports hormones from endocrine gland to their target glands and to tissues. Transports the waste products of cellular metabolism from tissues to excretory organs.

5. Regulation: It regulates acid base balance or PH through the distribution of buffer. It regulates body temperature by increasing or decreasing blood flow to the skin and through the heat absorbing or coolant properties of its water content.

6. P rotection: Phagocytic WBC and specialised plasma protein and antibodies protects the body against microorganism and toxins. Clotting mechanism protects against blood loss.

7. Components of blood Plasma: it is straw coloured , transparent fluid in which different types of cells are suspended. Components of plasma: Water (90-92%) Protein Other solutes

8. Water : It is needed to maintain the normal state of hydration: Water is a solvent for both extracellular and intracellular chemical reactions. Water in plasma is easily available to cell, tissue and cellular fluid of body.

9. b)Protein Albumin : Albumin is the most abundant plasma protein. It is synthesised in liver . It has following functions: 1 . It maintains the plasma osmotic pressure at its normal temperature. It promotes H₂O retention in blood which maintains normal blood volume and temperature.2. Albumin also acts as carrier molecule by binding to the molecule of other substances such as hormones .

10. Fibrinogen : It is also produced by liver and is essential for blood clotting. When fibrinogen and several other proteins involve in clotting, they are removed from plasma. The remaining liquid is called serum.

11. G lobuline: It is produced by plasma cell and liver. It is of three types , ẞ and  . and ẞ globulin’s function is to transport iron, lipid and fat soluble vitamins,  globulins are produced in lymphoid tissue. These are immuno -globulins and antibodies that help to prevent diseases like tetanus, polio and measles.  

12. c) Other solutes : Plasma electrolytes are inorganic salt or molecules that separate into cations and anions when they are dissolved in water . Cation : Major cation of plasma is sodium (Na) which has an important effect on osmotic pressure . Other cations are (K), (Mg) and (Ca² *). 2 . Anion: Principal anion is chloride (CI) , others are sulphate (So), iodine (I), bicarbonate (MCO).

13. The functions of electrolytes are as follows : 1 . They help in maintaining osmotic pressure . 2 . They serve as essential mineral . 3.They are involved in wide variety of activities like : Cell formation Contraction of muscles Transmission of nerve impulses Formation of secretions Maintenance of salt and alkali

14. B . Nutrients: Nutrients are the products of digestion that pass s into blood for the distribution to all body cells . Glucose : It appears in plasma in low concentration (70-110 dmg /100ml). It is the body's most rapidly available source of usable energy. 2 . Amino acids: They are important as they provide the building block for protein synthesis. They are used rapidly by body cells .

15. 3. Lipids: Lipids are found in plasma in the form of free fatty acid, phospholipid, triglycerides and cholestrol . Lipids act as a fuel in the body. They are important components of nerve cell and steroid hormone.

16. c. Gases: Oxygen, carbondioxide and nitrogen are the principal gases present in plasma. Oxygen and carbon- dioxide are also transported in combination with haemoglobin in RBCs . D. Waste Products: Waste products are the breakdown product of metabolism. These are urea, uric acid creatinine , bilirubin and ammonium salts . E. Regulatory Substances Enzymes: Regulatory sub stances enzymes are present in plasma . They regulate growth an development.

17. Red Blood Cells (Erythrocytes): RBCs are discotic -shaped cells constituting 99% of the blood and carrying haemoglobin molecules. Each cell is surrounded by a colourless envelope covering a semi-liquid material having 65% water and

18. 35% solids of which 33% constitutes haemoglobin bound to 2% stromal meshwork of protein, phospholipids, cholesterol, cholesterol esters, and neutral fat .

19. WBC (Leukocyte ) These are larger than RBCs. WBCs have a nuclei. These cells are able to move independently . They pass through blood vessels into the tissues. The WBCs are classified into two groups : 1 . Granulocyte 2. Agranulocyte

20. 1.Granulocyte :Most numerous WBCs are granulocyte. These are called granulocyte, because they contain large number of granules in the cytoplasm. Outside they have multi- lobed nuclei. Granulocytes have lobed nuclei. They are of three types : Neutrophils (60-70 %) Basophils (0.5-1%) Eosinophils (2-4%)

21. Neutrophils : These are phagocytes that engulf and destroy micro-organisms and other bacterias . Granules inside the cytoplasm are the packet of isozymes that ingest the foreign material, breakdown them and finally destroy them . The nuclei of neutrophils are of 2-6 lobes. The functions of neutrophils are: 1 . These protect against foreign material 2 . Remove waste material, e.g. cell debris.

22. 2. Basophils: These are bi-lobed , elongated, irregular shaped nucleus, found in the form of S. Granules are round in shape and variable in size. These cells contain heparin which prevents clotting of blood and histamine prevents infection . Basophils plays an important role in providing immunity against parasites.

23. 3. Eosinophils : These cells have B-shaped nuclei, usually have two lobes. Large granules are present in cytoplasm. Eosinophils are also phagocytic. Their amount increases during allergic reaction. They contain certain proteins called plasminogen which are the precursors of plasmin which breakdown the fibrin and help to dissolve blood clot.

24. 2. Agranulocytes : These are 20-30% of all WBCs. They have few non- specific lysosome granules in cytoplasm. These are of two types : 1 . Monocytes (3-8 %) 2. Lymphocytes (20-25%)

25. Monocytes: These are the largest blood cells. These are mobile, phagocytic, mono nuclear cells. The macrophages form an important portion of the reticulo endothelial system. These lie in the liver, lungs, lymph node thymus gland and bone marrow.

26. 2.Lymphocytes : These are smaller cells, mononuclear. Nucleus is small and slightly indended . Lymphocytes are of two types: 1.B-lymphocyte 2. T-lymphocyte B-lymphocyte originate in bone marrow. These cells produce antibody against specific antigen. T-lymphocyte attach to the bacteria, poison and chemical debris.

27. Functions of WBCs are : Phagocytosis Antibody Formation Fibroblasts Formation: at inflammation site Trephones Synthesis Heparin Secretion: basophils release heparin which blocks intravascular clotting. Antihistamine Function : granulocytes, rich in histamine are defensive against allergic conditions.

28. Platelets (Thrombocytes): They are very small, non-nucleated of diameter 2-4µm, obtained from cytoplasm of megakaryocytes in red bone marrow. Its constituents promote blood clotting leading to haemostasis (stop bleeding). Blood platelet count lies between 200x10'1 and 350x10 (2,00,000-3,50,000/mm³).

29. Functions of Platelets 1.Vasoconstriction : They become sticky and adhere to the damaged wall of blood vessel secreting serotonin that constrict (narrow) the vessel, thus lowering blood flow. 2.Platelet Plug Formation: This is a positive feedback mechanism, through which adhered platelets combine and attract passing platelets to the site of damaged vessel This produces a temporary seal, called the platelet plug.

30. 3.Coagulation ( Blood Clotting ): Blood clot is an insoluble thread-like mesh of fibrin that traps blood cells. Prothrombin activator acts on the plasma protein ( prothrombin ) forming thrombin that acts on fibrinogen (plasma protein) forming fibrin . 4.Fibrinolysis : Breakdown of the clot and healing of damaged blood vessel is the initial stage after the clot has formed. Healing process rebuilds the integrity of the blood vessel wall soon after the removal of clot.

31. B lood clotting Blood clotting is the process by which blood from its liquid state changes to a gel-like consistency. A host defence mechanism known as haemostasis isa complex process which block the bleeding from a damaged vessel. Platelet adherence and aggregation to macromolecules in the sub-endothelial tissues forms a primary haemostatic plug.

32. Blood clotting

33. Mechanism of blood clotting The process of coagulation can be summarised under three main heads : 1) Formation of Prothrombin 2) C onversion of Prothrombin to Thrombin 3) Conversion of Fibrinogen to Fibrin

34. 1)Formation of Prothrombin : Prothrombin is formed by two different mechanisms or pathways , extrinsic pathway and intrinsic pathway

35. I.Extrinsic Pathway: If the site of trauma is vascular wall or the tissues outside the blood vessels, prothrombin formation occurs by extrinsic pathway . It involves three steps : a) Release of Tissue Thromboplastins b) Activation of Factor X c) Formation of Prothrombin Activator Complex

36. Release of Tissue Thromboplastins : The damaged tissues release tissue thromboplastin (factor III). b) Activation of Factor X: The tissue thromboplastin (factor III ) combines with the stable factor (factor VII) to form the tissuethromboplastin -factor VII complex . This tissue thromboplastinfactor VII complex in the presence of Ca2 activates Stuart factor(factor X), forming activated factor X

37. c) Formation of Prothrombin Activator Complex: The activated factor X along with the labile factor (factor V) and Ca * (factor IV) forms a complex called prothrombin activator .

38. II. Intrinsic pathway: This mechanism of prothrombin formation initiates in the blood itself, in case of injury to blood tissue or exposure of blood to collagen (injured vascular wall). The steps of intrinsic pathway can be summarised as:

39. a. Injury to blood or tearing to collagen of underlying vascular endothelium activates plasma factor XII to initiates the intrinsic pathway . Simultaneously, platelets are also activated to release phospholipids . b. Factor XI is activated by the activated factor XII . C. Factor IX is activated by the activated factor XI in the presence of Ca

40. d) Factor X is activated by the activated factor IX . e) The activated factor X along with the phospholipids (released by the activated platelets), activated factor V and Ca2 forms a complex called prothrombin activator (or prothrombinase ).

41. 2) Conversion of Prothrombin to Thrombin: Prothombinase in the presence of Ca + convert prothrombin to thrombin , at the surface of platelets. As a result, platelets plug at the site of injury .

42. 3) Conversion of Fibrinogen to Fibrin : The formed thrombin acts as a proteolytic enzyme and converts fibrinogen to fibrin , in three steps: Thrombin acts as a proteolytic enzyme and converts fibrinogen to fibrinmonomer . Fibrin polymerises again to form a long chain of fibrin which forms a reticulum of clot.

43. iii) In the presence of fibrin stabilising factor (factor VIII) , covalent cross linkages are formed between fibrin threads ; and after injury blood capillaries are covered by it within 2-8 minutes.

44. Blood Grouping

45. Blood type or blood group is the classification of blood on the basis of the presence or absence of inherited antigens (proteins, carbohydrates, glycoproteins, or glycolipids) on the surface of RBCs .

46. Depending on the type of antigens present or absent on the membrane of RBCs, the various blood grouping systems are as follows : Classical ABO blood grouping system Rhesus (Rh) blood grouping system

47. ABO Blood: Group ABO blood group is based on A and B antigens on the RBCs surface. This system classifies blood on the basis of antigens located on the surface of RBCs and circulating antibodies in plasma. Combination of proteins and their antibodies form four types of blood:

48. 1) Type A: It consists of protein A and antibodies for protein B . 2 ) Type B: It consists of protein B and antibodies for protein A. 3 ) Type AB: It consists of proteins A and B but no antibodies . 4 ) Type O: It does not consist of any proteins but have both A and antibodies . Thus, type AB blood group is universal receiver and can receive any blood type; whereas type O blood group is universal donor and can donate blood to anyone.

49. Rh Blood Group It was first detected in Rhesus monkey . Sometimes surface antigens of RBCs have the Rh factor. 97% Indian population have Rh positive (i.e., presence of Rh antigens) else have Rh negative blood group .

50. Cross- Matching The procedure of cross-matching is performed before transfusing blood to determine whether the donor blood is compatible or incompatible with the recipient blood. Compatibility can be determined by matching different blood group systems (especially the ABO and Rh system), and/or by directly determining the presence of antibodies against a sample of donor tissues or blood.

51. Purpose : The procedure of cross-matching is the final step of pre-transfusion compatibility testing. Compatibility testing is done to detect the presence of irregular antibodies , errors in ABO grouping, and errors in patient identification and result recording. The procedure of cross-matching detects :

52. Most recipient antibodies directed against antigens on the donor RBCs . Major errors in ABO grouping, labeling, and identification of donors and recipients.

53. Principle: The procedure of cross-matching detects the incompatibilities between the donor and recipient that will not be evident on blood typing. There are two types of cross-matches , i.e., major cross-match and minor cross-match.

54. In the major cross-match , the patient's serum is tested with donor cells to determine whether the patient has an antibody that may cause a haemolytic transfusion reaction or may reduce the cell survival of donor cells.

55. In the minor cross-match , the patient's cells are tested with donor plasma to determine whether an antibody is present in the donor's plasma directed against an antigen on the patient's cells.