Blood

1. Blood Tahmina Yasmin Lecturer North South University

2. Definition Blood is a specialized fluid connective tissue consisting of some cells suspended in a liquid intercellular substance known as plasma.

9. Major functions of blood Transport of respiratory gases Transport of nutrients Act as vehicle Regulation of body temperature Regulation of water and electrolyte balance Maintenance of acid-base balance Excretory function Defensive action

10. Composition of blood Blood is composed of mainly two parts: Plasma Blood cells

11. PLASMA Plasma contains- 1)Water (92%) 2)Solid(8%) i) Inorganic constituents E.g. Na+, K+, Ca++, Mg++ etc. ii) Organic constituents a) Non protein nitrogenous substance e.g. urea, uric acid. b) Fats e.g. lipid, cholesterol c) Protein e.g. albumin, globulin (7%) d) Carbohydrate e.g. glucose, sucrose e) Coloring materials e.g. bilirubin

19. Function of plasma protein It helps in exchange of fluid between blood and tissue spaces. It is essential for the coagulation of blood. It acts as buffer and maintains acid-base balance. It helps in carriage of CO2 by forming carboamino protein. Gamma-globulin is antibody in nature and performed defensive action against infection. It helps in transport of lipid, hormone, drugs etc.

24. Erythrocyte/RBC Leukocyte/WBC Thrombocyte/Platelet BLOOD CELLS

25. Red blood cell (R.B.C) or Erythrocytes Characteristics The mature human R.B.C is - A circular, biconcave and non-nucleated (i.e. without any nucleus) cell. Soft and flexible and readily be squeezed through narrow capillaries. Internally composed of a framework which is built of many lipids and proteins and gap within the frame work is filled with hemoglobin. The membrane of the R.B.C is selectively permeable.

26. Composition i) Water : 65% ii) Solid : 35% a) Hemoglobin -33% b)Others e.g. protein, lipid, fat -2%

27. Erythropoesis Formation of red blood cells (R.B.C or erythrocytes) is known as erythropoesis. Red blood cells originate from the embryonic tissue (mesoderm) and the main sites of erythropoesis are bone marrow and spleen. The main factor influencing the red blood cells production is the oxygen content of the arterial blood. Decrease in oxygen content in the arterial blood decreases oxygen tension in the tissue, which is known as hypoxia.

28. Hypoxic state leads to the production of glyprotein called erythropoietin or haemopoetin, which is also known as erythrocyte stimulating factor (ESF). This factor is released from the renal tissue ( Juxtra glomerular cells or JG cells) and stimulates erythropoesis or red blood cell production from the bone marrow. The erythropoetin acts on the stem cells of bone marrow and converts it into haemocytoblasts which in turn converts into erythrocytes.

31. Factors essential for erythropoesis Protein: Food rich in first class protein is very necessary. These proteins are intended to supply the essential amino acids for the synthesis of globin portion of hemoglobin. Hypoxia: Low oxygen tension or level in the arterial blood provides a physiological stimulus for erythropoesis (red cell production) through the action of erythropoetin. Other maturation factors: Vitamin B12 (cyanocobalamin) and folic acid, some metals like Cu, Mn, Co, Ca, vitamin C, thyroxin hormone.

32. Fate of red blood cells After an average time period of 120 days, special cells known as reticulo-endothelial cells (R.E Cells) of liver and spleen engulf (swallow) the senile (old) red blood cells and break them. Hemoglobin is released and iron is freed from them . The freed iron is stored in the body as ferritin and haemosiderin, which help in the formation of new hemoglobin later on. The rest of the haem molecule is converted into some pigments such as bilirubin (yellow in color) and biliverdin (greenish in color).

35. Major functions of RBC Respiratory functions: Red cells carry oxygen ( from lungs to the tissue) and carbon dioxides (from tissue to the lungs). Acid-basebalance: Hemoglobin (and also the plasma protein) have got the buffering action and thus contribute to the acid base balance of plasma. Viscosityof blood: RBC helps to maintain the viscosity of blood. If RBC is increased in plasma, viscosity of blood will increase. Formationofpigments: Various pigments like bilirubin, biliverdin are derived from hemoglobin.

36. White blood cells/Corpuscles (W.B.C) or Leukocytes Characteristics: The mature human W.B.C has got the following characteristics: It lacks hemoglobin but contains nucleus. They are much less in number. Their average total number is 6000 to 8000 per cubic mm. They are amoeboid (i.e. amoeba like) Their life span is shorter (few days to month) These are produced from the lymphatic system.

37. Leukocytes (Greek: “White Hollows”) All WBCs (leukocytes) have a nucleus and no hemoglobin. Protect body against microorganisms and remove dead cells and debris. Granular or agranular classification based on presence of cytoplasmic granules made visible by staining. Types & Functions Granulocytes Neutrophils: Small phagocytic cells Eosinophils: Reduce inflammation Basophils: Release histamine and increase inflammatory response Agranulocytes Lymphocytes: Immunity Monocytes: Become macrophages

38. Neutrophils Features Neutrophils are the most abundant leukocytes in blood. Nuclei contains 2 to 5 lobes connected by thin strands. Neutrophils are Filled with granules (e.g. Lysosomes) Functions Give fastest response of all WBC to bacteria and parasites. Very active migration Sensitive to chemotactic factors which attract them to infection site Direct actions against bacteria release lysozymes which destroy/digest bacteria release defensin proteins that act like antibiotics release strong oxidants (bleach-like, strong chemicals ) that destroy bacteria

39. Eosinophils Features Generally larger than neutrophils Stain orange-pink with eosin Contain abundant basic protein Nucleus with 2 or 3 lobes connected by a thin strand Functions Leave capillaries to enter tissue fluid Release histaminase slows down inflammation caused by basophils Attack parasitic worms Phagocytize antibody-antigen complexes.

40. Basophil Features Least common leukocyte Stains with basic dyes Precursor of mast cells in tissues. Functions Involved in inflammatory and allergy reactions. Leave capillaries & enter connective tissue as mast cells. Release heparin, histamine & serotonin heighten the inflammatory response and account for hypersensitivity (allergic) reaction. Heparin is a potent anti-coagulant that does not allow clotting within vessels.

41. Monocyte (Agranulocyte) Features Nucleus is kidney or horse-shoe shaped Largest WBC in circulating blood does not remain in blood long before migrating to the tissues differentiate into macrophages. Fixed groups are found in specific tissues (alveolar macrophages in lungs, kupffer cells in liver. Wandering group gathers at sites of infection Functions Take longer to get to site of infection, but arrive in larger numbers Destroy microbes and clean up dead tissue following an infection

42. Lymphocyte (Agranulocyte) Features Dark, oval to round nucleus Cytoplasm sky blue in color 20 to 25% of circulating WBCs Functions B cells destroy bacteria and their toxins turn into plasma cells that produces antibodies T cells attack viruses, fungi, transplanted organs, cancer cells Natural killer cells attack many different microbes & some tumor cells destroy foreign invaders by direct attack

43. Differential WBC Count (DC) Detection of changes in numbers of circulating WBCs (percentages of each type) indicates infection, poisoning, leukemia, chemotherapy, parasites or allergic reaction Normal WBC counts TC (Total count): 5,000-10,000 / L DC (Differential count) neutrophils 60-70% (up if bacterial infection) lymphocyte 20-25% (up if viral infection) monocytes 3 -- 8 % (up if fungal/viral infection) eosinophil 2 -- 4 % (up if parasite or allergy reaction) basophil <1% (up if allergy reaction or hypothyroid)

44. Major functions Defensive action: Phagocytosis: The neutrophils and monocytes engulf foreign particles and microorganism. Antibody formation: Lymphocytes produce antibodies (mainly gamma globulin) and play an important role in defensive mechanism of the body. Secretion of heparin: The basophils secret heparin, which helps in the prevention of intravascular clot. Manufacture of trephones: Leukocytes produce some special protein like substance known as “trephones” which have great influence on nutrition, growth and tissue repair .

45. Platelets (Thrombocytes) Disc-shape cell fragment with no nucleus Platelets are the cell fragments pinched off from megakaryocytes in red bone marrow Platelets are important in preventing blood loss Platelet plugs Promoting formation and contraction of clots Platelets--Life History Platelets form in bone marrow by following steps: myeloid stem cells eventually become megakaryocytes whose cell fragments form platelets. Short life span (5 to 9 days in bloodstream) They are formed in bone marrow. They remain few days in circulating blood. Aged ones are removed by fixed macrophages in liver and spleen. Normal count: 2-4 lacs /cubic mm of blood.

46. Major functions Blood coagulation: When blood is shed, the platelets disintegrate and liberate thromboplastin, which activates prothrombin into thrombin. Repair of capillary endothelium: While in the circulation, the platelets adhere to the damaged cell lining of the capillaries and thus bring about a speedy repair.

47. HEMOGLOBIN Hemoglobin is a conjugated protein. It is the red pigment inside the red blood cells. It consists of two parts- Globin – 96% Haem – 4%. Normal count: In male : 14 – 18g/100ml of blood. In female : 12 – 15.5g/100ml of blood.

48. Function of hemoglobin It is essential for transport of O2 from lungs to the tissue and CO2 from tissue to the lungs. It is an important blood buffer and helps to maintain PH of the blood. Various pigments like bilirubin, biliverdin etc are derived from hemoglobin. It reserves iron and protein.

49. Structure of hemoglobin Hemoglobin α- Chain Globin β- Chain Fe++ Haem porphyrin ix

50. Haem From structural point of view, haem is a metalloporphyrin type of compound consisting of four pyrrole structures joined with one another with a ferrous iron (Fe++) in the center. Porphyrins are complex heterocyclic compound that contain a ring structure, which is formed by four pyrrole rings by methine (=CH-) bridges. The porphyrin ring present in haem molecule is known as protoporphyrin ix.