Hypersegmented Neutrophil.—A hyperseg-
mented neutrophil is a mature neutrophil. The
nucleus of a hypersegmented neutrophil is divided
into six or more segments or lobes (fig. 7-17).
EOSINOPHIL.—Eosinophils aid in detoxifi-
cation. They also break down and remove protein
material. The cytoplasm of an eosinophil contains
numerous coarse, reddish-orange granules, which are
lighter colored than the nucleus (fig. 7-17).
BASOPHIL.—The function of basophilic cells is
unknown. It is believed, however, that basophilic cells
keep the blood from clotting in inflamed tissue.
Scattered large, dark-blue granules that are darker than
the nucleus, characterize the cell as a basophil
(fig. 7-17). Granules may overlay the nucleus as well
as the cytoplasm.
LYMPHOCYTE.—The function of lymphocytes is
also unknown, but it is believed that they produce
antibodies and destroy the toxic products of protein
metabolism. The cytoplasm of a lymphocyte is clear sky
blue, scanty, with few unevenly distributed, azurophilic
granules with a halo around them (fig. 7-17). The nucleus
is generally round, oval, or slightly indented, and the
chromatin (a network of fibers within the nucleus) is
lumpy and condensed at the periphery.
MONOCYTE.—The monocyte, the largest of the
normal white blood cells, destroys bacteria, foreign
particles, and protozoa. Its color resembles that of a
lymphocyte, but its cytoplasm is a muddy gray-blue
(fig. 7-17). The nucleus is lobulated, deeply indented
or horseshoe-shaped, and has a relatively fine
chromatin structure. Occasionally, the cytoplasm is
more abundant than in the lymphocyte.
Materials Required for the Differential
Count Procedure
To perform a differential count, the following
materials are required:
Four plain glass microscope slides, clean and dry
Wright-Giemsa stain solution (follow
manufacturer’s directions for use and storage)
Staining containers
Deionized or distilled water
Microscope with light source
Immersion oil
Blood cell counter
Differential Count Procedure
The procedure for the differential white cell count
is done in 4 steps:
Step 1:
Making the blood smear
Step 2:
Staining the cells
Step 3:
Counting the cells
Step 4:
Reporting the count
Each step of this procedure will be discussed in the
following sections.
MAKING THE BLOOD SMEAR.—The
simplest way to count the different types of white cells
is to spread them out on a glass slide. The preparation
is called a blood smear. There are two methods of
making a blood smear: the slide method (covered in
this chapter) and the cover glass method.
It is very important to make a good blood smear. If
it is made poorly, the cells may be so distorted that it
will be impossible to recognize them. You should
make at least two smears for each patient, as the
additional smear should be examined to verify any
abnormal findings.
To prepare a blood smear for a differential count,
follow the steps below:
1. Using a capillary tube, collect anticoagulated
blood from a venous blood sample.
2. Deposit a drop of blood from capillary tube onto
a clean, grease-free slide. Then place the slide
on a flat surface, blood side up.
3. Hold a second slide between your thumb and
forefinger and place the edge at a 23-degree
angle against the top of the slide that holds the
drop of blood (see figure 7-18, view A). Back
the second slide down until it touches the drop of
blood. The blood will distribute itself along the
edge of the slide in a formed angle (see
figure 7-18, view B).
4. Push the second slide along the surface of the
other slide, drawing the blood across the surface
in a thin, even smear (see figure 7-18, view C).
If this is done in a smooth, uniform manner, a
gradual tapering effect (or “feathering”) of the
blood will occur on the slide. This “feathering”
of the blood is essential to the counting process
and is the principal characteristic of a good
blood smear (see figure 7-18, view D). When
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