White blood cells (WBCs) or leukocytes are the colorless
and nucleated formed elements of blood
(leuko is derived
from Greek word leukos = white).
Alternate spelling for
leukocytes is leucocytes.
Compared to RBCs, the WBCs are larger
in size
and lesser in number. Yet
functionally, these cells are
important like RBCs because of their
role in defense
mechanism of body and protect the body
from invading
organisms by acting like soldiers.
WBCs Vs RBCs
WBCs differ from RBCs in many aspects.
The differences
between WBCs and RBCs are given in
Table 16.1.
1. Larger in size.
2. Irregular in shape.
3. Nucleated.
4. Many types.
5. Granules are present in some type
of WBCs.
6. Lifespan is shorter.
CLASSIFICATION
Some of the WBCs have granules in the
cytoplasm.
Based on the presence or absence of
granules in the
cytoplasm, the
leukocytes are classified into two groups:
1. Granulocytes which have granules.
2. Agranulocytes which do not have
granules.
1. Granulocytes
Depending upon the staining property
of granules, the
granulocytes are
classified into three types:
i. Neutrophils with granules taking
both acidic and
basic stains.
ii. Eosinophils with granules taking
acidic stain.
iii. Basophils with granules taking
basic stain.
2. Agranulocytes
Agranulocytes have plain cytoplasm
without granules.
Agranulocytes are of
two types:
i. Monocytes.
ii. Lymphocytes.
MORPHOLOGY
OF WHITE BLOOD CELLS
NEUTROPHILS
Neutrophils which are also known as
polymorphs have
fine or small granules
in the cytoplasm. The granules take
acidic and basic stains. When stained
with Leishman’s
stain (which contains
acidic eosin and basic methylene
blue) the granules appear violet in
color.
Nucleus is multilobed (Fig. 16.1). The
number of
lobes in the nucleus depends upon the
age of cell. In
younger cells, the nucleus is not
lobed. And in older
neutrophils, the nucleus has 2 to 5
lobes. The diameterof cell is 10 to 12 μ (Table 16.2). The
neutrophils are
ameboid in nature.
EOSINOPHILS
Eosinophils have coarse (larger)
granules in the
cytoplasm, which stain pink or red
with eosin. Nucleus
is bilobed and spectacle-shaped.
Diameter of the cell
varies between 10 and
14 μ.
BASOPHILS
Basophils also have coarse granules in
the cytoplasm.
The granules stain purple blue with
methylene blue. Nucleus is bilobed. Diameter of the cell is 8 to
10 μ.
MONOCYTES
Monocytes are the largest leukocytes
with diameter of 14 to 18 μ. The cytoplasm is clear without granules. Nucleus
is round, oval and horseshoe shaped, bean shaped or kidney shaped. Nucleus is
placed either in the center of the cell or pushed to one side and a large amount
of cytoplasm is seen.
LYMPHOCYTES
Like monocytes, the lymphocytes also
do not have granules in the cytoplasm. Nucleus is oval, bean-shaped or
kidney-shaped. Nucleus occupies the whole of the cytoplasm. A rim of cytoplasm
may or may not be seen.
Types of Lymphocytes
Depending upon the size, lymphocytes
are divided into two groups:
1. Large lymphocytes: Younger
cells with a diameter of 10 to 12 μ.
2. Small lymphocytes: Older
cells with a diameter of 7 to 10 μ.
Depending upon the function,
lymphocytes are divided into two types:
1. T lymphocytes: Cells
concerned with cellular immunity.
2. B lymphocytes: Cells
concerned with humoral immunity.
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