Ok, Let S Have a Quick Review Before We Get to the Good Stuff!

Hematology Ok, let’s have a quick review before we get to the “good” stuff!

Components of Blood

 90% Water and 10% dissolved substances  Volume in adults about 6 quarts (5.5L)  45% to 50% of blood volume consists of formed elements, the remainder is plasma o Chief functions of formed elements are: . Delivery of substances needed for cellular metabolism . Defense against invading microorganisms and injury . Acid-base balance Plasma and Plasma Proteins . Accounts for 55%-60% of blood volume . Concentration of elements varies depending on diet, metabolic demand, hormones and vitamins. . Plasma differs from serum: Serum is plasma that has been altered in lab. to remove fibrinogen. . Plasma proteins account for 7% of total plasma weight o 3 major groups:  Albumins: concentration of 4g/dl, essential for regulating passage of water and solutes, provide critical colloid osmotic or oncotic pressure  Globulins or Immune globulins: synthesized by mature lymphocytes called plasma cells in the lymphoid organs, chiefly the lymph nodes; critical for defense against infectious microorganisms; include IgA, IgG, IgM, IgD, IgE  Clotting factors: fibrinogen the most plentiful; promote coagulation and stop bleeding; other plasma proteins include: complement proteins which are involved in immune response, variety of enzymes and their inhibitors, and specific carriers of such elements as iron and copper. Plasma lipids triglycerides, phospholipids, cholesterol and fatty acids are carried through the blood as complexes with plasma proteins (known as lipoproteins) Cellular Components: . Erythrocytes: function as a gas carrier; most abundant cells of blood, occupy 48% in men and 42% in women; two properties are bioconcavity and reversible deformability. . Leukocytes: (white blood cells) defend the body against organisms that cause infection and remove debris; classified according to structure: o Granulocytes: (contain many membrane-bound granules in their cytoplasm), contain enzymes capable of killing microorganisms and catabolizing debris, granules also have function in immune and d inflammatory response; capable of ameboid movement by which they migrate through vessel walls (diapedesis) o Neutrophil: (polymorphonuclear neutrophil or PMN): most numerous of granulocytes constituting about 55% of total leukocytes in adults; reach a fully mature state in bone marrow (marrow neutrophil reserve); chief phagocyte of early inflammation; immature neutrophils are bands or stabs. o Eosinophils: 1%-4% of normal leukocyte count; capable of ameboid movement and phagocytosis; ingest antigen-antibody complexes; induced by IgE-mediated hypersensitivity reactions to attack parasites; help control inflammatory process. o Mast cells: large cells, cytoplasmic granules contain histamine, chemo- tactic factors and cytokine; act rapidly to make blood vessels more permeable; central cell in inflammation; found in high concentrations in vascularized connective tissues; Mastocytosis: increased accumulation of mast cells. o Basophils: make up less than 1% of leukocytes; cytoplasmic granules contain vasoactive amines: histamine, bradykinin, and serotonin and an anticoagulant: heparin. o Agranulocytes: do not contain lysosomal granules in their cytoplasm; made up of:  Monocytes: largest blood cell; precursors of macrophages; ingest and process antigens so that antigens can be recognized by T and B lymphocytes; able to release tissue thromboplastin and to activate plasminogen, proteolytic enzymes, and other agents.  Macrophages: initiate inflammatory response  Lymphocytes: constitute approx. 36% of total leukocyte count; primary cells of immune response; types: T cells, B cells, and mature B cells (plasma cells); life span days, months, or years depending on type or subtype.  Natural killer (NK) cells: resemble lymphocytes; kill some types of virus-infected cells without prior exposure to them and tumor cells in vitro; account for 5%-10% of circulating lymphoid pool; found mainly in peripheral blood and spleen. . Platelets: not cells; disk-shaped cytoplasmic fragments; essential for blood coagulation and control of bleeding; no nucleus, no DNA; thrombopoietin (TPO) main regulator of circulating platelet mass; approx. 140,000-340,000 platelets per mm of circulating blood with additional one third of the body’s available platelets in a reserve pool in the spleen.

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Lymphoid Organs . Spleen: largest of secondary lymphoid organs o Functions: mononuclear phagocytes filter and cleanse the blood; lymphocytes mount an immune response to blood-borne microorganisms; serves as a blood reservoir. . Lymph Nodes: part of lymphatic system, thousands clustered around lymphatic veins o Function: site of activity or development of large numbers of lymphocytes, monocytes and macrophages; cleanses lymph system of foreign particles and microorganisms.

Mononuclear Phagocyte System . Consists of a line of cells that originate in the bone marrow . Transported by bloodstream . After differentiation into monocytes, settle in tissue as mature macrophages . Composed of monoblasts, promonocytes, and monocytes in bone marrow, monocytes in peripheral blood, and macrophages in tissue (see Table 25-3 pg. 900 for list of various names given to macrophages localized in specific tissues).

Hematopoiesis . Blood cell production; occurs in liver and spleen of the fetus, after birth normally only occurs in bone marrow (medullary hematopoiesis). . Two stage process: mitotic division (or proliferation) and maturation (or differentiation). . Each type of blood cell has parent cells or stem cells. . Stem cells undergo mitosis when they receive specific biochemical signals indicating that populations of circulating blood cells have diminished to a certain point. . Stem cells continue to proliferate until the requisite number of mature daughter cells has entered the circulation. . Stem cells of lymphocytes and possibly monocytes are stimulated by other mechanisms, particularly activation of the immune response. . Two separate pools in bone marrow: the stem cell pool and the bone marrow pool, with eventual release of mature cells into the peripheral circulation

So, let’s get into the good stuff already!