Hypersegmented Neutrophil.—A hyperseg-mented neutrophil is a mature neutrophil. Thenucleus of a hypersegmented neutrophil is dividedinto six or more segments or lobes (fig. 7-17).EOSINOPHIL.—Eosinophils aid in detoxifi-cation. They also break down and remove proteinmaterial. The cytoplasm of an eosinophil containsnumerous coarse, reddish-orange granules, which arelighter colored than the nucleus (fig. 7-17).BASOPHIL.—The function of basophilic cells isunknown. It is believed, however, that basophilic cellskeep the blood from clotting in inflamed tissue.Scattered large, dark-blue granules that are darker thanthe nucleus, characterize the cell as a basophil(fig. 7-17). Granules may overlay the nucleus as wellas the cytoplasm.LYMPHOCYTE.—The function of lymphocytes isalso unknown, but it is believed that they produceantibodies and destroy the toxic products of proteinmetabolism. The cytoplasm of a lymphocyte is clear skyblue, scanty, with few unevenly distributed, azurophilicgranules with a halo around them (fig. 7-17). The nucleusis generally round, oval, or slightly indented, and thechromatin (a network of fibers within the nucleus) islumpy and condensed at the periphery.MONOCYTE.—The monocyte, the largest of thenormal white blood cells, destroys bacteria, foreignparticles, and protozoa. Its color resembles that of alymphocyte, but its cytoplasm is a muddy gray-blue(fig. 7-17). The nucleus is lobulated, deeply indentedor horseshoe-shaped, and has a relatively finechromatin structure. Occasionally, the cytoplasm ismore abundant than in the lymphocyte.Materials Required for the DifferentialCount ProcedureTo perform a differential count, the followingmaterials are required:Four plain glass microscope slides, clean and dryWright-Giemsa stain solution (followmanufacturer’s directions for use and storage)Staining containersDeionized or distilled waterMicroscope with light sourceImmersion oilBlood cell counterDifferential Count ProcedureThe procedure for the differential white cell countis done in 4 steps:Step 1: Making the blood smearStep 2: Staining the cellsStep 3: Counting the cellsStep 4: Reporting the countEach step of this procedure will be discussed in thefollowing sections.MAKING THE BLOOD SMEAR.—Thesimplest way to count the different types of white cellsis to spread them out on a glass slide. The preparationis called a blood smear. There are two methods ofmaking a blood smear: the slide method (covered inthis chapter) and the cover glass method.It is very important to make a good blood smear. Ifit is made poorly, the cells may be so distorted that itwill be impossible to recognize them. You shouldmake at least two smears for each patient, as theadditional smear should be examined to verify anyabnormal findings.To prepare a blood smear for a differential count,follow the steps below:1. Using a capillary tube, collect anticoagulatedblood from a venous blood sample.2. Deposit a drop of blood from capillary tube ontoa clean, grease-free slide. Then place the slideon a flat surface, blood side up.3. Hold a second slide between your thumb andforefinger and place the edge at a 23-degreeangle against the top of the slide that holds thedrop of blood (see figure 7-18, view A). Backthe second slide down until it touches the drop ofblood. The blood will distribute itself along theedge of the slide in a formed angle (seefigure 7-18, view B).4. Push the second slide along the surface of theother slide, drawing the blood across the surfacein a thin, even smear (see figure 7-18, view C).If this is done in a smooth, uniform manner, agradual tapering effect (or “feathering”) of theblood will occur on the slide. This “feathering”of the blood is essential to the counting processand is the principal characteristic of a goodblood smear (see figure 7-18, view D). When7-21
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