PYS 203: Blood PDF

PYS 203: BLOOD DR. TORYILA J.E  What is Blood? Blood is a connective tissue in fluid form. Blood consists of the acellular portion, a yellowish fluid, called plasma in which cellular constituents (Red Blood Cells, White Blood Cells and Platelets) are suspended. 8% of the mean fraction...

PYS 203: BLOOD DR. TORYILA J.E  What is Blood? Blood is a connective tissue in fluid form. Blood consists of the acellular portion, a yellowish fluid, called plasma in which cellular constituents (Red Blood Cells, White Blood Cells and Platelets) are suspended. 8% of the mean fraction of Body Weight is blood.  Its volume is 5-6 L in males and 4-5 L in females BLOOD is slightly alkaline, with a pH of ~ 7.4 Its color varies from bright to dark red It has a salty metallic taste Specific gravity of total blood : 1.052 to 1.061 Osmolarity: 300 mOsm Salanity: 0.9% COMPOSITION OF BLOOD Blood Plasma Components (55%) 90% Water Proteins 8% w/v – Albumin (60 %): Produced by the liver Maintain osmotic pressure Transport hormones and enzymes  Blood Plasma Components (55%) Proteins 8% w/v – Globulins (36%) : Alpha and Beta Globulins: produced by the liver, transport lipids, metals and fat soluble vitamins Gamma Globulins: Antibodies released by plasma cells in response to immune response Fibrinogens (4%): Produced by the liver, form fibrin fibers of blood clots Gas Electrolytes: Na+, K+, Ca2+, Mg2+, Cl-, SO4-, HCO3 Maintain plasma osmotic pressure and pH FUNCTIONS 3 major functions Transportation Regulation Protection  DISTRIBUTION FUNCTIONS Delivering O2 and nutrients to body cells Transporting metabolic wastes to lungs and kidneys for elimination Transporting hormones from endocrine organs to target organs  REGULATION FUNCTIONS Maintaining body temperature by absorbing and distributing heat Maintaining normal pH using buffers; alkaline reserve of bicarbonate ions Maintaining adequate fluid volume in circulatory system  PROTECTION FUNCTIONS Preventing blood loss Plasma proteins and platelets initiate clot formation Preventing infection Antibodies Complement proteins WBCs Erythrocytes – Red Blood Cells (RBCs) Biconcave discs, anucleated, essentially no organelles Oxygen-transporting cells 7.5 µm in diameter (diameter of capillary 8 – 10µm) Most numerous of the formed elements Females: 4.3 – 5.2x1012/L Males: 5.2 – 5.8 x1012/L Made in the red bone marrow in long bones, cranial bones, ribs, sternum, and vertebrae Average lifespan 100 – 120 days  „ ROULEAUX FORMATION When blood is taken out of the blood vessel, the RBCs pile up one above another like the pile of coins. This property of the RBCs is called rouleaux (pleural = rouleau) formation It is accelerated by plasma proteins globulin and fibrinogen. „ SPECIFIC GRAVITY Specific gravity of RBC is 1.092 to 1.101. „ PACKED CELL VOLUME Packed cell volume (PCV) is the proportion of blood occupied by RBCs expressed in percentage. It is also called hematocrit value. It is 45% of the blood and the plasma volume is 55% Hematocrit: % of erythrocytes volume to the total blood volume. Normal hematocrit values in healthy males is 47% ± 5% and in females it is 42% ± 5% Adult males: 42% to 51% Adult females: 36% to 47%. Infants: 32% to 42% Newborns: 45% to 61%  Red blood cells have a unique structure. Their flexible disc shape helps to increase the surface area-to-volume ratio of these extremely small cells. This enables oxygen and carbon dioxide to diffuse across the red blood cell's plasma membrane more readily. Red blood cells contain enormous amounts of a protain called hemoglobin. ERYTHROCYTES Structural characteristics contribute to gas transport Biconcave shape—huge surface area relative to volume >97% hemoglobin A red blood cell has what is known as a biconcave. No mitochondria; ATP production anaerobic; do not consume O2 they transport RBCs dedicated to respiratory gas transport Hemoglobin binds reversibly with oxygen Normal values Males - 13–18g/dl; Females - 12–16 g/dl  Antigens are embedded in the cell membrane, they decide the blood group of an individual. The RBC cytoplasm provides energy to maintain intracellular homeostasis This energy is generated mostly through anaerobic glycolysis  Red cells do not contain mitochondria and can therefore not readily metabolize glucose aerobically and produce the ATP that way. The metabolism of the human red blood cell consists of the Glycolytic pathway (Embden-Meyerhof pathway) and the Hexose Monophosphate shunt. For the red blood cells the pathways protect the haemoglobin molecule, the membrane lipids and structural proteins from oxidative stress. They also assist in the structural integrity of the red cell, and regulate the volume of the cell. These metabolic networks are also different to others in the respect that the red cell does not generate biomass: its main task is to produce the necessary cofactors (ATP, NADPH, and NADH) for maintaining its osmotic balance and electro-neutrality and fighting oxidative stresses ERYTHROCYTE METABOLISM Importance of glycolysis in red cells: Energy production: it is the only pathway that supplies the red cells with ATP. Reduction of methemoglobin: glycolysis provides NADH for reduction of metHb by NADH- reductase In red cells 2,3 Disphosphoglycerate binds to Hb, decreasing its affinity for O2, and helps its availability to tissues.  The erythrocyte sedimentation rate (ESR) is a common hematological test for nonspecific detection of inflammation that may be caused by infection, some cancers and certain autoimmune diseases. It can be defined as the rate at which Red Blood Cells (RBCs) sediment in a period of one hour PCV HAEMATOCRIT Hematocrit (HCT) and packed cell volume (PCV) are used to measure red blood cell mass. An increase in red blood cell mass is equivalent to erythrocytosis and a decrease indicates an anemia. PCV The packed cell volume (PCV) is a measurement of the proportion of blood that is made up of cells. The value is expressed as a percentage or fraction of cells in blood The PCV increases when the number of red blood cells increases or when the total blood volume is reduced, as in dehydration. Low PCV indicating anaemia, when your body decreases its production of red blood cells or increases its destruction of red blood cells, or the blood cells are diluted by increases in total volume (haemodilution, for example occurring during pregnancy). Haemocytometry quantitatively measures the number of RBCs in a blood sample using the RBC count method. RBCs are counted manually using a haemocytometer or Neubauer’s chamber ,RBC Pipette, RBC-Diluting Fluid(Formalin Citrate solution) Osmotic fragility The osmotic fragility test demonstrates increased RBC fragility in blood specimens in which the RBCs havedecreased surface area-to-volume ratios. Blood is added to a series of tubes with increasingly hypotonicsodium chloride (NaCl) solutions  Clinical Significance Elevated values high OFT= increased V / SA associated with: Hereditary spherocytosis - Acquired immune Hemolytic - Anemia with Spherocytesis Hereditary stomatocytrsis  Osmotic Fragility Test ▪ Measures the resistance of RBCs to hemolysis by osmotic stress ▪ Determines the resistance of the red cell to hemolyis in varying concentrations of hypotonic solutions. ▪ Gives an indication of the surface area: volume ratio of erythrocytes SA:V ratio ▪ Results of OFT are increased in blood sample ( erythrocytes) with decrease SA / V ratio ▪ Useful in the diagnosis & confirmation of hereditary spherocytosis. WHAT IS HAEMATOPOIESIS? Is the process involved in the production of all blood cells from the pluripotent stem cell; The hematopoietic stem cells (HSC). The word Haemopoiesis refers to the production and development of all the blood cells: Erythrocytes: Erythropoiesis Leucocytes: Leucopoiesis Thrombocytes: Thrombopoiesis.  HAEMATOPOIESIS (HAEMOPOIESIS) Blood cell formation Haematopoiesis begins at a very early stage in embryonic development, at about 3 weeks in the human. At a later stage of embryogenesis (after about week 6 in humans) haematopoiesis occurs mainly in the liver and at birth shifts to the bone marrow (BM). IN Adult, haemopoiesis Occurs in red bone marrow. STEM CELLS These cells have extensive proliferative capacity and also the: Ability to give rise to new stem cells (Self Renewal) Ability to differentiate into any blood cells lines (Pluripotency) They grow and develop in the bone marrow. The bone marrow & spleen form a supporting system, called the “hemopoietic microenvironment” Cell hierarchy (Haemopoiesis schematic representation) Role of growth factors in normal haemopoiesis  ERYTHROID PROGENITOR CELLS BFU-E: Burst Forming Unit – Erythrocyte: Give rise each to thousands of nucleated erythroid precursor cells, in vitro. Undergo some changes to become the Colony Forming Units-Erythrocyte (CFU-E) Regulator: Burst Promoting Activity (BPA) ERYTHROPOIESIS As myeloid stem cell transforms Ribosomes synthesized Hemoglobin synthesized; iron accumulates Ejection of nucleus; formation of reticulocyte (young RBC) Reticulocyte ribosomes degraded; Then become mature erythrocytes Reticulocyte count indicates rate of RBC formation Production of Erythrocytes: Erythropoiesis  ERYTHROPOIETIN A hormone produced by the Kidney. A circulating Glycoprotein Nowadays available as Synthetic Epoietin Acts mainly on CFU – E. Increases the number of: Nucleated precursors in the marrow. Reticulocytes & Mature Erythrocytes in the blood.  ERYTHROPOIETIN ▪Activates stem cells of bone marrow to differentiate into pronormoblasts. ▪Shortening cell cycle. ▪Decrease maturation time. ▪Increases rate of mitosis and maturation process. ▪Increases rate of hemoglobin production. ▪Causes increased rate of reticulocyte release into the peripheral blood, (normally the reticulocyte when it is released to the peripheral blood it need only one day to mature to RBC). ▪Prevent apoptosis.  Regulation and Requirements for Erythropoiesis The number of RBCs remains constant and reflects a balance between RBC production and destruction. Erythropoiesis is hormonally controlled and depends on adequate supplies of iron, amino acids, and B vitamins. Erythropoietin (EPO) is synthesized mainly from kidneys. Liver and BM macrophages may be also a source of Epo. Epo is secreted in response to anoxia caused for example by anemia or high altitude HAEMOGLOIN Haemoglobins are coagulated protein consisting 2α- and 2β- globin chains each with its own iron containing haem group. The α- chains contains 141 amino acids with β- chains containing 146 amino acids. HAEMOGLOBIN RBC has 640 million Hb molecules MW of Hb 640 million Daltons Consists of 4 polypeptide chains 2 alpha + 2Beta Chains Haem = protoporphyrin + Fe NORMAL HAEMOGLOBIN Function of heamoglobin is to transport oxygen to the tissues Normal haemoglobin mainly HBA, HBF, HBA2 HBA 2 alpha chains + 2 Beta chains Haemoglobin disorders give rise to haemoglobinopathies eg sickle cell disease HAEMOGLOBINOPATHIES HbS – the most common being sickle cell anaemia. Hb molecule has an abnormal β chain, in which valine replaces glutamine in the 6th position of the β-chain of globin. Thalassaemias – this group of disorders is characterized by failure to synthesize normal quantities of Hb. The disorder is termed α or β – thalassaemia, depending upon which chain is synthesized in reduced quantities. HbSS, HbSC, HbM and HbE are some abnormal haemoglobin that occurs due to mutation.  FORMATION OF HAEMOGLOBIN Erythroblasts in the bone marrow undergo mitosis and begin making haemoglobin, first by synthesizing haem and the polypeptide chains of globin separately and then by combining them to form heamoglobin. Synthesis of haem begins in the mitochondria with the condensation of sussinyl coenzyme A and glycine to form δ-amino lavulinic acid.  Each haem molecule combines with polypeptide chain, a globin synthesized by ribosomes, forming a subunit of haemoglobin called a chain (MW – 16,000). Four of these bind together loosely to form the whole haemoglobin molecule. A disruption at any point in the synthesis of haemoglobin can result in the following disorders: Iron deficiency anemia Thalassemia Sideroblastic anemia  PHYSIOLOGICAL VARIATIONS. Increase in RBC Count Increase in the RBC count is known as polycythemia. It occurs in both physiological and pathological conditions. When it occurs in physiological conditions it is called physiological polycythemia. The increase in number during this condition is marginal and temporary. It occurs in the following conditions Age Sex High altitude Muscular exercise Emotional conditions Increased environmental temperature  Decrease in RBC Count Decrease in RBC count occurs in the following physiological conditions: High barometric pressures At high barometric pressures as in deep sea, when the oxygen tension of blood is higher, the RBC count decreases. During sleep RBC count decreases slightly during sleep and immediately after getting up from sleep. Pregnancy In pregnancy, the RBC count decreases. It is because of increase in ECF volume. Increase in ECF volume, increases the plasma volume also resulting in hemodilution.  PATHOLOGICAL VARIATIONS Pathological polycythemia is the abnormal increase in the RBC count Polycythemia is of two types, the primary polycythemia and secondary polycythemia. Polycythemia Vera Primary polycythemia is otherwise known as polycythemia vera. It is a disease characterized by persistent increase in RBC count. This is always associated with increased white blood cell count. Polycythemia vera occurs in myeloproliferative disorders like malignancy of red bone marrow Secondary Polycythemia:Respiratory disorders,Congenital heart disease  ANEMIAS What is anemia ? What are the bases for Classification of anemia? How do you diagnose anemia ?  Abnormal decrease in RBC count is called anaemia Anaemia is a functional inability of the blood to supply the tissue with adequate O2 for proper metabolic function. Anaemia will occur if there is reduction in RBC count, Hb content and packet cell volume. Anemia—a condition in which hemoglobin (Hb) concentration and/or red blood cell (RBC) numbers are lower than normal and insufficient to meet an individual’s physiological needs  Anaemia may develop: When RBC loss or destruction exceeds the maximal capacity of bone marrow RBC production When bone marrow production is impaired  CLASSIFICATION OF ANAEMIA Anaemia is classified by two methods: Etiological classification (causes of the anaemia) Anemia caused by blood loss Anemia caused by decreased production or production of faulty red blood cells Anemia caused by the destruction of red blood cells  Etiological Classification: on the basis of the causes, anaemia can be classified as follows: Haemorrhagic anaemia Haemolytic anaemia Nutrition deficiency anaemia Aplastic anaemia Anaemia of chronic disease  Anemia : etiology, iron deficiency, vitamin A deficiency, folate deficiency, B12 deficiency, riboflavin deficiency, malaria, infection, infectious disease, schistosomiasis, hookworm, intestinal helminths, HIV, tuberculosis, obesity, overweight, undernutrition, underweight, stunting, wasting, child development, anemia of inflammation; anemia of chronic disease; thalassemia, α-thalassemia, β-thalassemia; sickle cell disease; sickle cell disorders; hemoglobinopathies  Iron-Deficiency Anaemia Iron is essential for the various activities of the human body especially in the haemoglobin synthesis. Iron deficiency anaemia is a condition in which the body has too little iron in the bloodstream. This form of anaemia is more common in adolescents and in women before menopause. Haemolytic Anaemia Haemolytic anaemia is a condition in which red blood cells are destroyed and removed from the bloodstream before their normal lifespan is up. Haemolytic anaemia can affect people of all ages, races and sexes. Aplastic anaemia is a blood disorder in which the body’s bone marrow doesn’t make enough new blood cells. This may result in a number of health problems including arrhythmias, an enlarged heart, heart failure, infections and bleeding. Damage to the bone marrow’s stem cells causes aplastic anaemia  Morphological classification Base of the size shape of the Red Blood Cell. Normocystic normochromic anaemia. The size and Hb content of RBC are normal.E.g Haemorrhagic anaemia Macrocytic normochronic anaemia – RBCs are large in size with normal haemoglobin content. E.g Megaloblastic anaemia Macrocytic hypochronic anaemia – RBC are large in size. The Hb content in the cell (MCH) is less. E.g vitamin B12 deficiency anemia Microcytic hypochronic anaemia – In this type of anaemia, the RBCs are smaller in size and the Hb content (MCH) is less. Iron deficiency anaemia  LABORATORY DIAGNOSIS FBC, reticulocyte count, thin Blood film. B12, folate, hemoglobin electrophoresis Bone marrow aspirate to assess possible defective hematopoiesis Others: thyroid function tests, EPO, Cytokines. Red cell indices play a vital role in classification of anemia Red cell indices are MCV – Mean Corpuscular Volume MCH – Mean Corpusculat Hemoglobin MCHC – Mean Corpuscular Hemoglobin Concentration RDW – Red Cell Distribution Width  MCV is defined as the volume of the average red blood cell expressed in femtoliters. MCH is the mass of hemoglobin red cells expressed in pictograms. MCHC is the measure of the concentration of hemoglobin in a given volume of PRC expressed as g/L. The RDW is a measure of variation of red cell size or anisocytosis LEUCOCYTES AND IMMUNITY  LEUCOCYTES (WHITE BLOOD CELLS) The leucocytes, also known as white blood cells are the mobile units of the blood’s protective system. They are partially formed in the bone marrow and partially in the lymph tissue. Classified according to the presence or absence of granules and the staining characteristics of their cytoplasm. Leucocytes appear brightly colored in stained preparations, they have a nuclei and are generally larger in size than RBC’s.  STRUCTURE OF WBC · Are nucleated · Contain organelles · Diameters range from 8 – 24 μm · May contain cytoplasmic granules (agranulocytes vs. granulocytes) WHITE BLOOD CELLS WBC: mobile units of the body's protective system. Normal count is 4.0-11.0x109/L Types: Granulocytes (Polymorphnuclear): Neutrophils 40-60 % Eosinophils 2-4 % Basophils 0.4-1 % Agranulocytes (mononuclear): Lymphocytes 20-30 % Monocytes 2-5 %  FUNCTIONS OF WBC They squeeze through the pores of the capillaries by diapedesis. They move toward the site of infection by amoeboid movement. Different chemicals released by microbes and inflamed tissues attract neutrophils and macrophages→ chemotaxis.  PHAGOCYTOSIS Definition: Cellular ingestion of the offending agent. Most important function of neutrophils and macrophages. Selective process. Phagocytosis is increased if: Surface of particle is rough. Lacks protective protein coat. Binding of antibodies to antigen (opsonization).  Lymphocytes are responsible for acquired immunity. They are present in lymph nodes and other lymphoid tissues throughout the body. B lymphocytes: Processed in bone marrow. When exposed to an Ag, they differentiate to plasma cells that produce antibodies (gamma globulins). This initiates the destruction of the antigen. T lymphocytes: Processed in thymus. They release chemicals that destroy target cells with which they make contact such as virus infected cells and cancer cells. GRANULOCYTES: Granules contain lysosomal enzymes and Neutrophil (also called a defensins polymorphonuclear cell) Neutrophils are quick · diameter = 10-12 μm acting phagocytes (1st · cytoplasmic granules stain pale responders) lavender · lobed nuclei (3-6 lobes) · % of total leukocytes: 50-70%  Granules contain digestive Eosinophil enzymes · diameter = 10-14 μm Are antiparasitic · large granules which stain red Phagocytize immune (major basic protein) complexes · bilobed nucleus Anti-allergy · represent 2-4% of the total WBC count Basophil · diameter = 8-10μm · large granules which stain blue · U or S shaped nucleus · 0.4 – 1% of total WBC BASOPHIL contain: Histamine- which induces inflammation and vasodilation heparin- an anticoagulant  MONOCYTES Diameter = 18 μm Nucleus is U shaped or kidney shaped Abundant pale blue cytoplasm 3 – 8 % of the total WBC Are phagocytes – slow but strong Develop into macrophages when they migrate into connective tissue  Agranuloctes: lack visible cytoplasmic granules Lymphocyte: diameter 5-8 μm (small), 10-12 μm (medium) or 14-17 μm (large) 20-25 % of the total WBC count large, deep blue or slightly indented nucleus thin rim of pale blue cytoplasm T lymphocyte (T cells) fight antigens directly B lymphocytes (B cells) divide to produce plasma cells that secrete antibodies Leucopoiesis is the production of leucocytes ·All leukocytes can be made in red bone marrow from hemocytoblasts ·Lymphocytes can be made in either red bone marrow or lymphoid tissues ·The production of lymphocytes is stimulated by interleukins and by colony stimulating factors (CSFs)  The immune system A functional system – NOT an organ system: Complex system – includes Skin – physical barrier Lining of mucus membranes – physical barrier Secretions – tears, mucus etc - antimicrobial Blood cells and vasculature – WBCs Bone marrow Liver – makes complement proteins Lymphatic system and lymphoid organs Most tissues – have resident immune cells  Immunity Immunity is body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells consists of following activities: Defense against invading pathogens (viruses & bacteria) Removal of 'worn-out' cells (e.g., old RBCs) & tissue debris (e.g., from injury or disease) Identification & destruction of abnormal or mutant cells (primary defense against cancer) Rejection of 'foreign' cells (e.g., organ transplant) Inappropriate responses: Allergies - response to normally harmless substances Autoimmune diseases Characteristics of Immunity Recognition of self versus non-self Response is specific Retains a “memory” allowing an accelerated second response Can respond to many different materials Involves lymphocytes and antibodies  IMMUNE SYSTEM Innate (non-adaptive) first line of immune response relies on mechanisms that exist before infection Acquired (adaptive) Second line of response relies on mechanisms that adapt after infection handled by T- and B- lymphocytes  Active Immunity The production of antibodies against a specific disease by the immune system. Naturally acquired through disease Artificially acquired through vaccination Vaccines include inactivated toxins, killed microbes, parts of microbes, and viable but weakened microbes. Active immunity is usually permanent  A vaccinated person has a secondary response based on memory cells when encountering the specific pathogen. Routine immunization against infectious diseases such as measles and whooping cough, and has led to the eradication of smallpox, a viral disease. Unfortunately, not all infectious agents are easily managed by vaccination.  Passive Immunity Passive Immunity- Protection against disease through antibodies produced by another human being or animal. Effective, but temporary E.G. Maternal antibodies Innate immunity vs Adaptive Immunity Innate Immunity Adaptive Immunity (first line of defense) (second line of defense) No time lag A lag period Not antigen specific Antigen specific No memory Development of memory Immune System Response to Antigens Humoral Immunity Involves antibodies (secreted from B cells) dissolved in the blood plasma. Demonstrated as a immune response using only the blood serum. Defense against bacteria, bacterial toxins, & viruses.  B Cells Produce and mature in bone marrow Migrate to the lymphoid tissues Involved in humoral immunity Once activated by antigen, proliferate into two clones of cells: plasma cells that secrete antibodies and memory cells that may be converted into plasma cells at a later time  Immune System Response to Antigens Cell-Mediated Immunity Involves the activities of specific white blood cells (T cells). Defense against cancer cells, virus-infected cells, fungi, animal parasites, & foreign cells from transplants. T- Cells Produce and mature in thymus Thymosin Involved in cell-mediated immunity Activated when another cell presents antigen to them Several types of T cells: cytotoxic T cells, helper T cells, suppressor T cells, and memory T cells  ANTIBODIES Antibodies, also called immunoglobulins or Igs [with molecular weights of 150–900 Md], constitute the gamma globulin part of the blood proteins. They are soluble proteins secreted by the plasma of B cells. The antibodies inactivate antigens by, Complement fixation (proteins attach to antigen surface and cause holes to form, i.e., cell lysis), Neutralization (binding to specific sites to prevent attachment, Agglutination (clumping), Precipitation (forcing insolubility and settling out of solution).  NATURAL KILLER CELLS Not B-lymphocytes / T-lymphocytes Important part of the innate immune system Kill virus /bacteria infected cells (Intracellular pathogens) Kills cancer cells Complement System Complement consists of more than 20 proteins present in plasma and on cell surfaces that interact with each other to produce biologically active inflammatory mediators that promote cell and tissue injury The first component of complement is named C1 (etc.) When cleaved: fragments of complement components are designated by small letters (e.g. C3a and C3b) THE COMPLEMENT SYSTEM The complement system is a major triggered enzyme plasma system. It coats microbes with molecules that make them more susceptible to engulfment by phagocytes. Vascular permeability mediators increase the permeability of the capillaries to allow more plasma and complement fluid to flow to the site of infection. They also encourage polys to adhere to the walls of capillaries (margination) from which they can squeeze through in a matter of minutes to arrive at a damaged area. Once phagocytes do their job, they die and their "corpses," pockets of damaged tissue, and fluid form pus.  Complement Pathways 3 pathways for activation: Classical: most specific (antibody dependent activation, binds C1) Lectin binding: some specificity (mannose binding protein, binds C4) Alternative: most primitive (non-specific, auto-activation of C3)  Complements Function: Anaphylatoxins: C3a and C5a: mast cell degranulation smooth muscle contraction mast cell degranulation mediator release (histamine, leukotrienes) vascular changes: dilation, increased permeability (edema) C5a also leukocyte adhesion and chemotaxis (recruitment) Opsonization: C3b, C3bi, C3d: (binding to complement receptors and enhanced phagocytosis by neutrophils and macrophages) Clearance of circulating immune complexes Membrane attack complex: C5b-C9 (cell lysis)  FAILURE OF IMMUNE RESPONSE Immune response can fail hypersensitivity reactions overreaction to infectious agents Allergy overreaction to environmental substances Autoimmunity -overreaction to self Immunodeficiency Loss or inadequate function of various components of the immune system The immuno-compromised host has an impaired function of immune system is at high risk of infection OTHER IMMUNE CELLS Cytokines Interleukins Interferons Chemokines Defensins Platelet-activation factor Tumor Necrosis Factors  PLATELET Platelets or thrombocytes are small colorless, non nucleated cells. Shape is spherical or rod shaped and become oval or disc shaped when inactivated. Size: 1 to 4 micrometers in diameter. Life span: 8-12 days  lipid bilayer Glycoprotein receptors Cell Membrane of Platelet It is 6 nm thick and contain lipids (phospholipids, cholesterol and glycolipids),Carbohydrates(glycocalyx), Proteins and glycoproteins. All glycoprotein and phospholipids are functionally important. Phospholipids accelerate the clotting reactions. The phospholipids form the precursors of thromboxane A2 and other prostaglandin-related substances  Glycopropteins Prevents the adherence of platelets to normal endothelium. Accelerates the adherence of platelets to collagen and damaged endothelium in ruptured blood vessels. Forms a receptor for ADP and thrombin.  Platelet production (thrombopoiesis) Megakaryocytes release platelets into circulating blood Rate of platelet formation is stimulated by thrombopoietin, thrombocyte-stimulating factor, interleukin-11, and Multi-CSF  Development: From the pluripotentstem cells in the bone marrow. CFU-M Colony forming megakaryocytes Megakaryoblast Promegakaryoctye Megakaryocytes Platelets Thrombopoiesis  PROPERTIES OF PLATELETS Platelets have three important properties Adhesiveness Aggregation Agglutination.  Platelet functions Transporting chemicals important to clotting Forming temporary platelet plug in walls of damaged blood vessels Contracting after a clot has formed Phagocytosis PDGF PAF Transfusion as Blood products 1.Define haemostasis. 2.Describe the main mechanisms that prevent blood loss after an injury. 3.Describe role of platelets in haemostasis. 4.Outline the mechanism of platelet plug formation. HAEMOSTASIS The objects of the complex hemostatic process are: To maintain the composition and fluidity of the blood within the blood vessels, To seal leaks in the blood vessels and stem or stop blood loss, To restore normal vascular structure or effectively repair the scar tissue. WHAT IS HAEMOSTASIS ? Blood clotting or coagulation is a biological process that stops bleeding. Blood clotting is the transformation of liquid blood into a semisolid gel. Clots are made from fibers (polymers) of a protein called fibrin Hemostasis is the process in which bleeding is stopped. It involves three steps Primary Haemostasis Platelet Plug Formation Dependent on normal platelet number & function Secondary Hemostasis Activation of Clotting Cascade  Deposition & Stabilization of Fibrin Tertiary Hemostasis Dissolution of Fibrin Clot Dependent on Plasminogen Activation  Haemostasis There are 3 mechanisms that work together to stop the flow of blood. They are Vasoconstriction Platelet plug formation Clotting of blood Vasoconstriction of a damaged blood vessel slows the flow of blood and thus helps to limit blood loss. This process is mediated by: Local controls. Vasoconstrictors such as thromboxane are released at the site of the injury. Systemic control. Epinephrine released by the adrenal glands stimulates general vasoconstriction.  Formation of a Platelet Plug. When a blood vessel is damaged, the blood is exposed to collagen fibers in the basement membrane of the vessel. Platelets stick to collagen and become activated. Activated platelets release chemicals such as ADP, and thromboxane, that cause the aggregation of more platelets to the site of injury. Platelet aggregation results in the formation of a platelet plug which acts to stem the flow of blood from the broken vessel. It is essential that platelets become activated only at the site of a broken vessel.  The extrinsic pathway is triggered by a chemical called tissue factor that is released by damaged cells. This pathway is "extrinsic" because it's initiated by a factor outside the blood vessels. It's also known as the tissue factor pathway. The intrinsic pathway is triggered by blood coming into contact with collagen fibers in the broken wall of a blood vessel. It's "intrinsic" because it's initiated by a factor inside the blood vessel. It's sometimes called the contact activation pathway Fibrinolysis Enhance degradation of clots Activation of endogenous protease Plasminogen (inactive form) is converted to Plasmin (active form) Plasmin breaks down fibrin clots Function of Fibrinolysis in Homeostasis Fibrinolysis is the system whereby the temporary fibrin clot is systematically and gradually dissolved as the vessel heals in order to restore normal blood flow. Is the body’s defense against occlusion of blood vessels  Physiologic Inhibitors of coagulation Antithrombin III Activated Protein C + protein S Inactivates Va and VIIIa (via proteolysis) Thrombomodulin (glycoprotein) Binds to thrombin Decreases ability to produce fibrin Increases ability to activate Protein C  THROMBOSIS Thrombosis or intravascular blood clotting refers to coagulation of blood inside the blood vessels. Normally, blood does not clot in the blood vessel  CAUSES OF BLEEDING DISORDERS Hemophilia A and B are X-linked disorders, limited to males. The factor concentration in carriers is about half of the normal Female carriers with low levels of F VIII or F IX, predispose them to excessive bleeding Vitamin K deficiency Vitamin K is essential to the maturation of several clotting factors including factor X and prothrombin. In the absence of vitamin K these clotting factors are defective and thus inhibit the clotting mechanism. People with a Vitamin K deficiency experience excessive bleeding DIAGNOSIS OF BLEEDING DISORDERS Clotting Time Bleeding Time Platelet Count Platelet aggregation studied  ABO AND RHESUS BLOOD GROUP SYSTEM Objectives Describe the basis of blood grouping Know the ABO and Rh systems for blood grouping and their clinical significance. Describe incompatibilities in ABO and Rh systems. Know the different types of blood transfusions and transfusion reactions. Describe the basis of blood grouping and a safe blood transfusion  ABO BLOOD GROUP History Landsteiners discovered the ABO Blood Group System in 1901 He and five co-workers began mixing each others red blood cells and serum together and accidentally performed the first forward and reverse ABO groupings. Landsteiners Law: If an antigen (Ag) is present on a patients red blood cells the corresponding antibody (Ab) will NOT be present in the patients plasma, under ‘normal conditions’. Individual’s will form immune antibodies to ABO blood group antigens they do not possess.  Basis of Blood grouping (Multiplicity of Antigens in the blood cells) At least 300 commonly occurring antigens have been found on the cell membrane of RBCs. These can cause Ag-Ab reaction if mixed with plasma that contain Ab against these Ag. According to presence or absence of these antigens blood is classified into several groups or types. Two groups of Ag can cause transfusion reactions more than others: ABO and Rh systems of Ag  ABO BLOOD GROUP Agglutinogens refer to the antigens present on the cell membranes of red blood cells (RBCs). A variety of antigens are present on the cell membrane, but only a few of them are of practical significance. Agglutinins refer to the antibodies against the agglutinogens. These are present in the plasma. Agglutination of RBCs can be caused by the antigens present on their cell membranes in the presence of suitable agglutinins (antibodies). That is why these antigens are called agglutinogens  ABO BLOOD GROUP Almost all normal healthy individuals above 3-6 months of age have “ naturally occurring Abs” to the ABO Ags that they lack These “naturally occurring” Abs are mostly IgM class. That means that, they are Abs capable of agglutinating saline/ low protein suspended red cell without enhancement and may activate complement cascade.  The inheritance of the ABO blood group was demonstrated that each individual inherits one ABO gene from each parent and these two genes determine which Ags are present on RBCs membrane One position or Locus, on each chromosome number nine is occupied by an A, B, or an O gene  Genetics Two genes inherited, one from each parent. Individual who is A or B may be homozygous or heterozygous for the antigen. Heterozygous: AO or BO Homozygous: AA or BB Phenotype is the actual expression of the genotype, ie, group A Genotype are the actual inherited genes which can only be determined by family studies, ie, AO.  ABO blood group Relative frequency of different blood groups O- 47% A -41% B- 9% AB -3%  Group O No A or B antigens present, These individuals form potent anti-A and anti-B antibodies which circulate in the blood plasma at all times. Group A No B antigens present. These individuals form potent anti-B antibodies which circulate in the blood plasma at all times. Group B No A antigens present. These individuals form potent anti-A antibodies which circulate in the blood plasma at all times.  Group AB group AB. Both A and B antigens present. These individuals possess no ABO antibodies. If an individual is transfused with an incompatible blood group destruction of the red blood cells will occur. This may result in the death of the recipient. Summary Blood Group Antigens on cell Antibodies in Transfuse with plasma group A A Anti-B A or O B B Anti-A B or O AB A and B none AB, A, B or O O None Anti-A & B O  RHESUS BLOOD GROUP SYSTEM Rh is the most important blood group system after ABO in transfusion medicine. One of the most complex of all RBC blood group systems with more than 50 different Rh antigens. This unit will concentrate on the most COMMONLY encountered observations, problems and solutions. ⚫ Rh system IDENTIFIED by Landsteiner and Wiener in 1940. ⚫Immunized animals to Rhesus macaque monkey RBCs. ⚫Antibody agglutinated 100% of Rhesus and 85% of human RBCs  Antigens of Rh System ⚫ Terms “D positive” and “D negative” refer only to presence or absence of the Rh antigen D on the red blood cell. ⚫ Four additional antigens: C, c, E, e. ⚫ The Rh antigens and corresponding antibodies account for majority of unexpected antibodies encountered. ⚫ Rh antibodies stimulated as a result of transfusion or pregnancy, they are immune.  Importance of Blood Grouping Medically blood grouping is important to avoid blood transfusion reaction by transfusing compatible blood. Both ABO and Rhesus incompatibility can cause erythroblastosis fetalis. Blood grouping is necessary before marriage. Blood grouping is helpful in medicolegal cases like maternal and paternal disputes. Blood grouping is necessary for blood donation. The donor and the recipient blood group must be known. Blood grouping is necessary for organ transplant since many tissues and organs also have these antigens.  Summary Rh system second to ABO in transfusion medicine. Correct interpretation of D is essential to prevent immunization of D negative which may result in HDN. Most polymorphic of all blood group systems. Of the five antigens only yu78ghyug D testing is required.