Blood Cells

BLOOD CELLS

ERYTHROCYTES OR RED BLOOD CELLS (RBCS) RBC is a circular, biconcave, non nucleated disc. Life span of RBCs is 120 days. Size of RBC -6.5 -8.8 micron The central part of RBC is thinner then the circumference

RBC Count: At birth: 6-8 million/cumm Adults: 5-6 million/cumm Females 4.5- 6 million/cumm

FUNCTIONS z Transport of oxygen. z Helps in identifying the blood groups.

RBC indices: 1. MCV volume of RBC in cubic microns.(Normal range 78 – 94 cubic microns) < 78cubic micron -microcytes, > 94 cubic micron macrocytes. 2. MCH: Amount of hemoglobin in a single RBC in pico gm. Normal range: 28 -32 pg. 3. MCHC: Concentration of hemoglobin in a single RBC (NORMAL -32-35%) MCHC < 33% HYPOCHROMIC RBC NOTE: MCHC is never greater than 38% as RBC can not carry Hb beyond their saturation point. Thus anemia can never be hyperchromic

HAEMOPOIESIS It is the development of the blood cells ie. RBC, WBC and platelets ERYTHROPOIESIS Stages of erythropoiesis

STEM CELLS

PROERYTHROBLAST

EARLY NORMOBLAST

INTERMEDIATE NORMOBLAST

LATE NORMOBLAST

RETICULOCYTES

ERYTHROCYTES

CHANGES IN RBC DURING ERYTHRPOISIES 1. Reduction in cell size 2. Increased amount of cytoplasm 3. Basophilic cytoplasm changes to polychromatophilic and then acidophilic due to decreased content of RNA 4. Disappearance of nucleus

APPLIED 1. Anemia- When RBC counts are < 4 million/mm3 or Hb content <12gm % in females and < 13 gm % in males, then this condition is called anemia. Graded as: Mild Anemia 8 – 12 gm % Moderate Anemia - 5 – 8 gm% Severe Anemia - < 5 gm% 1. 2. 3. 4.

Based on cause anemia is divided into: Hemorrhagic anemia Hemolytic anemias Anemia due to dietary deficiency Aplastic anemia

Based on RBC size and hemoglobin concentration: 1. Megaloblastic anemias z Folic acid deficiency z Pernicious anemia. 2. Microcytic hypochromic anemia z Iron deficiency anemia z Thalassemia. Polycythemia: RBC COUNT > 6milllion/cumm. It is the condition characterized by excess number of RBC in the blood. PRIMARY POLYCYTHEMIA: Bone marrow is hyperplastic with increased number of RBC SECONDARY POLYCYTHEMIA: There is a compensatory increase in the red cells in chronic hypoxic conditions.

LEUCOCYTES OR WHITE BLOOD CELLS (WBC) 1. 2. 3. 4.

Leucocytes are colorless due to the absence of hemoglobin. Large in size than RBC's Size: 8 -15 micrometers. They possess a nucleus. Total count - 6000 to 11000/ cumm. of blood.

Divided into two types: 1. Granular Leucocytes 2. Non granular Leucocytes 1. Granular Leucocytes: The cells have granules in their cytoplasm and nucleus with two or more lobes. They are of three types: a) Eosinophils: Cells have a bilobed nucleus. They take up a red acid dye called eosin. b) Basophils: Cells take up a basic dye called methyl blue. They have a bilobed nulceus. c) Neutrophils: They take up neutral dye and have a multilobed nucleus. 2. Non granular Leucocytes: Do not have granules in their cytoplasm. They have unilobed nucleus. 1. Lymphocytes: Cells have round nucleus, scanty cytoplasm, formed in bone marrow. They are of two types: T -lymphocytes, B lymphocytes. 2. Monocytes : They have large cells with a kidney shaped nucleus. Functions 1. Neutrophils: Provide the body with a defense against infecting microorganisms by destroying them through phagocytosis. 2. Eosinophils: They phagocytose the particles which are formed when antigen and antibodies react. 3. Basophils: They destroy the products of antigen antibody reaction. 4. Lymphocytes are responsible for development of immunity against foreign substances or antigens in the form of antibodies. 5. Monocytes: They are actively motile and phagocytose in action and they destroy the invading microorganism by phagocytosis.

PLATELETS 1. Smallest colorless / spherical oval or rounded granulated bodies 2. Size: 2 -5 micrometer in diameter.

NORMAL COUNT: 1.5 – 4 Lac/cumm. Life span of platelets is 8 – 12 days. THROMBOPOIESIS: Process of development of platelets The process takes place in bone marrow. Steps of thrombopoeisis are: Pleuripotent stem cell

Committed stem cell

Megakaryoblast.

Promegakaryocyte

Granular megakaryocyte

Platelets.

Platelets are destroyed in spleen. FUNCTIONS OF PLATELETS 1. 2. 3. 4.

Coagulation of blood. Hemostasis or spontaneous arrest of bleeding. Storage and transport of molecules like histamine and serotonin. Retraction of clot.

Applied 1. Increased platelets: Thrombocytosis. Due to stress, trauma. Removal of spleen. 2. Low platelet count: Thrombocytopenia. Due to hypersplenism. Suppression of production by bone marrow. Infections.

BLOOD COAGULATION When any blood vessel is damaged blood escapes and after a few minutes the blood flow stops as it thickens and forms a clot. This process is called coagulation or clotting of blood. Different events in blood coagulation are: THROMBOPLASTIN ( FROM TISSUE AND PLATELETS) PROTHROMBIN

THROMBIN CALCIUM IONS (IN PLASMA) FIBRINOGEN

The various factors responsible for blood coagulation are: I FIBRINOGEN. II PROTHROMBIN. III THROMBOPLASTIN. IV CALCIUM. V ACCELERATOR GLOBIN. VII STABLE FACTOR.

FIBRIN(CLOT)

VIII ANTIHAEMOPHILIAC FACTOR. IX CHRISTMAS FACTOR. X STUART- POWER FACTOR. XI PLASMA THROMBOPLASTIN ANTECEDENT. XII HAGEMAN FACTOR. XIII FIBRIN STABILISING FACTOR. NOTE: THERE IS NO FACTOR VI. ANTICOAGULANTS A. NATURAL z HEPARIN z ANTI THROMBIN z PROTEIN C B. SYNTHETIC z VITAMIN K ANTAGONISTS eg. Dicoumarol. z CALCIUM CHELATORS like EDTA, remove calcium from blood and maintain the fluid state of blood.