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Kharkov National Medical University BLOOD Department of histology, cytology and embryology 2013 medical students Blood: consists of «Cells»: • Erythrocytes (RBC) • Leucocytes (WBC) • Thrombocytes (Platelets) + Plasma (fluid intercellular space) “Cells” of the BLOOD Blood cells. Erythrocytes ERYTHROCYTES Amount in blood Men - 3.9 - 5.5 ×1012/liter Women - 3,7-4,9 ×1012/liter Erythrocyte : • biconcave disc with average diameter ~ 7 µm (!!!). • does not contain a nucleus • is filled with hemoglobin - the oxygen binding protein function of ERYTHROCYTE: • carries oxygen from the lungs to the body cells, • helps in carrying of CO2 from tissues to the lungs • !!! NOTE: biconcave shape improves exchange by decreasing of diffusions distance !!! ERYTHROCYTES erythrocytes abnormalities : • an erythrocyte, smaller than 6 µm in diameter is termed a microcyte; • whereas an erythrocyte larger than normal (from 9 µm to 12 µm in diameter) is termed a macrocyte Thus a shift in size range toward smaller erythrocytes is called a microcytic condition, and toward bigger ones, a macrocytic condition. Smears of normal blood usually exhibit an occasional erythrocyte of abnormal shape. The general term for such a cell is a poikilocyte (Gr. poikilis, manifold). Unisocytosis and Poikilocytosis • 1 — discocytes normocytes; • 2 — MACROCYTE; (may be microcyte, 2 types of un-iso-cytosis) • 3,4 — echinocytes; • 5 — stomatocyte; • 6 — sferocytes. 1 3 • 3-6 - poikilocytosis 6 5 Platelets Platelets They are: • membranebound sacs, fragments of cells; • 2 to 5 µm in diameter. PLATELETS Platelets Play a Key Role in the Arrest of Bleeding (Hemostasis, blood clotting) Platelets Platelets • Consist of 2 zones: • - peripheral one is called the Hyalomere. • The central one Granulomere. • Hyalomere is a colorless and homogeneous. • granulomere contains azure-colored granules. Platelets • The granules contain several different substances: • thromboplastin – promotes blood clotting • serotonin – elicits pain • platelet-derived growth factor (PDGF) stimulates tissue regeneration Leucocytes • True cells, have nucleus, organelles and inclusions in granules • ALL Leucocytes migrare from blood to connective tissue • Nucleus containes two to eight lobes Classification: types by presence of granules !!! Totally 5 types of leucocytes Granulocytes • neutrophils, • basophils, • eosinophils A-granulocytes • monocytes, • lymphocytes Basophils Basophils • The basophilic granules are large, stain deep blue to purple, • and are often so numerous that they mask the nucleus. • Basophils constitute only approximately 0.5% of peripheral blood leukocytes. Basophils • These granules contain histamine (cause vasodilation) and heparin (anticoagulant). Eosinophils Eosinophils • have large acidophilic granules which appear pink (or red). • The granules contain digestive enzymes that are particularly effective against parasitic worms • These cells also phagocytize antigen-antibody complexes. Eosinophils EM image Neutrophils Neutrophils • 12 to 14 µm in diameter. • Granules are pale staining (neutral) • They play primary role in inflammation. • They are capable for phagocytosis of bacteria. The segmented nucleus of most neutrophils consists of two to five lobes interconnected by fine strands of chromatin. In mature neutrophils, sex chromatin (where present) can sometimes be seen as a separate tiny lobe known as a drumstick appendage. The cytoplasm of mature neutrophils contains two kinds of granules azurophilic granules and specific granules Neutrophil, phagocyte Lymphocytes LEUKOCYTES Lymphocytes comprise 20% to 50% of the blood leukocytes Lymphocytes • Nucleus is very large, almost fills the cell leaving a very thin rim of cytoplasm. • Function - immune response. • 2 types: • The B-lymphocytes: go to connective tissue to become PLASMA Cell. produce antibodies, • The T-lymphocytes act against virus-infected cells and tumor cells. Lymphocytes Monocytes Monocytes • - are the largest among the leukocytes, about 20 µm in diameter and agranular. • The nucleus is most often U-shaped or kidney-bean -shaped, or C-shaped • the cytoplasm is abundant and light blue. Monocytes comprise from 3% to 11% of the blood leukocytes Monocytes • These cells leave the blood stream to become macrophages in conn. tiss. • macrophages play a role in inflammatory and immune responses. • are antigen-presenting cells (APC) • They are phagocytes, defend the body against viruses and bacteria. Complete Blood Count (CBC) Characteristics Hematocrit men Hematocrit women RBC men RBC women Hb men HB women WBC Platelets Amount 0,39-0,49 0,35-0,45 4,0-5,0 х 1012/L 3,9-4,7 х 1012/L 13-16 g/dL 12-14 g/dL 4-9 х 109/L 180-320 х 109/L White Blood Cell Differential Count Basos Eos 0-1% 0,55% Segs Myelocytes Metamyelocytes Bands --- --- 1-6% Lymphs Monos Segmented 47-72% 19-37% 3-11% Blood Cell formation (haemocytopoiesis) Haemopoiesis • During fetal development, the formation of blood cells (haemopoiesis) begins in the wall of the yolk sac. • After the second month of fetal development, the liver, and, slightly later, the spleen, become the dominant sites of haemopoiesis. • From the 6th month the formation of blood cells occurs in bone marrow, Haemopoietic Cells • There are 6 classes of Haemopoietic Cells 1 class • Stem cells – 1-st class • -- self-replicating, which can generate all types of blood cells. 2 class • Progeny of stem cells may develop into either lymphoid semi-stem cells (gives rise to lymphocytes) or myeloid semi-stem cells (gives rise to the major groups of blood cells other than lymphocytes ) Note: semi-stem cells: • - are particularly determined cells: are capable to develop only into lymphocytes or only into all other blood cells. • Development of blood cells from LSC is called lymphopoiesis. • Development of blood cells from MSC is called myelopoiesis. 3 class is called • unipotential or … • hemopoietin-sensitive cells. Myeloid lines Myeloid semi-stem cell forms 4 kinds of hemopoietin-sensitive cells: • Erythropoietin-sensitive cell forms the erythroid line • Leukopoietin-sensitive cell forms granulocytes line • Monopoietin-sensitive cell forms monocyte macrophages line • Thrombopoietin-sensitive cell forms megakaryocytes --- thrombocyte line Lines of lymphopoiesis • B- lymphopoiesis • T- lymphopoiesis 4-th class of Haemopoietic Cells • The first recognizable, actively dividing cells that are called blast cells. 4. Haemopoietic Cells There are six types of blast cells: • Proerythroblast or simply erythroblast; • Myeloblast; • B- lymphoblast; • Megakaryoblast; • Monoblast • T- lymphoblast; 5th class of Haemopoietic Cells • - cell differentiation 6th class of Haemopoietic Cells • Mature cell - leave RBM and Thymus and go to bloodstream Erythroid line • The first identifiable stage of erythropoiesis is the proerythroblast - a large, slightly basophilic cell, which contains a large, lightly stained nulceus. Erythrocytes • Proerythroblasts differentiate to: • • • • basophilic erythroblast, polychromatophilic and orthochromic normoblasts. The nucleus is finally extruded from the normoblast. See: Erythrocytes of frog, • Nucleated • Primitive! • In human – only during formation, in bone marrow normoblasts Reticulocyte • young erythrocytes still contain some organelles, • … may enter circulation • … remain for a few days in the bone marrow to mature to erythrocytes Reticulocyte Erythrocyte is leaving RBM Granulocytes • Myeloblasts proliferate to generate promyelocytes. • Promyelocytes begin to accumulate nonspecific granules, but they are still able to divide. The maturation of their progeny, • … the Myelocytes, young leucocytes, are characterised by the accumulation of specific granules and changes in nuclear morphology. • Metamyelocytes have C-shaped nucleus. Blood Platelets (Thrombocytes) • Are formed from giant myeloid cells called megakaryocytes (60 to 160 µm in diameter). • Cytoplasmic processes of these cells extend into marrow sinuses and fragment away. These cellular fragments are the platelets or thrombocytes. • Megakaryocytes are in turn the product of the differentiation of basophilic megakaryoblasts.