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Histology Dr. Abdulla aaid Blood is a specialized connective tissue composed of formed elements and a fluid component (the extracellular matrix) known as plasma. The formed elements are composed of cells and cell fragments, known as platelets(erythrocytes RBCs, Leukocytes WBCs and Platelets) . Plasma : composition of plasma : a- plasma protein (Albumin alpha, beta, gamma globuin and fibrinogen ). b- Inorganic salts . 1 Histology Dr. Abdulla aaid c- Organic compounds (Amino acid ,Vitamins , hormones , lipoprotins , etc.) Erythrocytes (RBCs) : 1-Biconcave disks . 2- without nucli. 3-Surrounded by a plasma elements . 4- Survive in the circulation for about 120 days . Erythrocytes (RBCs) Leukocytes (WBCs) : Classification on the basis of the type of granule in the cytoplasm and the shape of the nucleus . 1- Granulocytes 2- Agranulocytes . 1- Granulocytes (polymorphonuclear leukocytes ) a- Neutrophils b- Eosinophils c- Basophiles . 2- Agranulocytes (Mononuclear leukocytes ): a- Lymphocytes b- monocytes Leukocytes : 1- Are spherical , no motile cells when in suspension in the circulating blood . 2- Capable of becoming flattened and motile on encountering a solid substrate. 3- Are involved in the cellular and humoral defense against foreign material . 2 Histology Dr. Abdulla aaid ** Diapedesis : Leukocytes leave the capillaries by passing between endothelial cells and penetrating the connective tissue . Leukocytes : 1- Neutrophils ( polymorphonuclear leukocytes ): It is nucleus consists 2-5 lobes . 2- the lobes are linked to each other by fine threads of chromatin . 3- immature Neutrophils a non segmented nucleus in the shape of a horseshoe . Eosinophils : 1- Are much less numerous than neutrophils . 2- Contains a bilobed nucleus . 3- Presence of many large granules . 4- A major function is phagocytosis and disposal of antigen – antibody complexes . Neutrophils & Eosinophils : * Eosinophilia :An increase in the number of eosinophils in blood which is associated with allergic reactions and helminthic (parasitic ) infections . 3 Histology Dr. Abdulla aaid Basophiles : 1- the nucleus is divided into irregular lobes . 2- Have a less heterochromatic nucleus . 3- Basophilic granules contain heparin and histamine . 4- Capable of amoeboid movement and phagocytosis . Basophiles Lymphocytes : 1- lymphocytes differentiate into T or B lymphoc 2- The cytoplasm is scanty , it appears as a thin rim around nucleus . Lymphocytes Monocytes : 1- bone marrow –derived a granulocytes . 2- the nucleus is oval horse shoe –shaped or kidney –shaped and eccentrically placed . Monocytes : 4 Histology Dr. Abdulla aaid 3- Monocytes cross the capillary walls and enter the connective tissue , then differentiate into macrophages . Platelets (Thrombocytes). 1- Are non nucleated , disk like cell fragmentswhich originated from megakaryocyte . 2- They promote blood clotting and help repair gaps in the walls of blood vessels , preventing loss of blood . Platelets (Thrombocytes). 5