Chapter 17
Blood
641
17
Te neutrophil cytoplasm contains very fine granules (of two
varieties) that are difficult to see (±able 17.2 and
Figure 17.10a
).
Neutrophils get their name (literally, “neutral-loving”) because
their granules take up both
basic
(blue) and
acidic
(red)
dyes
. ±o-
gether, the two types of granules give the cytoplasm a lilac color.
Some of these granules contain hydrolytic enzymes, and are re-
garded as lysosomes. Others, especially the smaller granules, con-
tain a potent “brew” of antimicrobial proteins, called
defensins
.
Neutrophil nuclei consist of three to six lobes. Because of
this nuclear variability, they are oFen called
polymorphonu-
clear leukocytes
(
PMNs
) or simply
polys
(
polymorphonuclear
5
many shapes of the nucleus).
Neutrophils are our body’s bacteria slayers, and their num-
bers increase explosively during acute bacterial infections such
as meningitis and appendicitis. Neutrophils are chemically at-
tracted to sites of inflammation and are active phagocytes. Tey
are especially partial to bacteria and some fungi, and bacterial
killing is promoted by a process called a respiratory burst. In
the
respiratory burst
, the cells metabolize oxygen to produce
potent germ-killer oxidizing substances such as bleach and hy-
drogen peroxide. In addition, defensin-mediated lysis occurs
when the granules containing defensins merge with a microbe-
containing phagosome. Te defensins form peptide “spears”
that pierce holes in the membrane of the ingested “foe.”
Eosinophils
Eosinophils
(e
0
o-sin
9
o-filz) account for 2–4%
of all leukocytes and are approximately the size of neutrophils.
Teir nucleus usually resembles an old-fashioned telephone
receiver—it has two lobes connected by a broad band of nuclear
material (±able 17.2 and ²igure 17.10b).
Large, coarse granules that stain from brick red to crim-
son with acid (eosin) dyes pack the cytoplasm. Tese granules
are lysosome-like and filled with a unique variety of digestive
erythrocytes. Tey characteristically have lobed nuclei (rounded
nuclear masses connected by thinner strands of nuclear mate-
rial), and their membrane-bound cytoplasmic granules stain
quite specifically with Wright’s stain. ²unctionally, all granulo-
cytes are phagocytes to some degree.
Neutrophils
Neutrophils
(nu
9
tro-filz), the most numerous
white blood cells, account for 50–70% of the WBC population.
Neutrophils are about twice as large as erythrocytes.
Formed
elements
(not drawn
to scale)
Platelets
Leukocytes
Erythrocytes
Differential
WBC count
(All total 4800–
10,800/
u
l
)
Neutrophils (50–70%)
Lymphocytes (25–45%)
Eosinophils (2–4%)
Basophils (0.5–1%)
Monocytes (3–8%)
Agranulocytes
Granulocytes
Figure 17.9
Types and relative percentages of leukocytes in
normal blood.
Erythrocytes comprise nearly 98% of the formed
elements, and leukocytes and platelets together account for the
remaining 2
1
%.
(a) Neutrophil:
Multilobed nucleus,
pale red and blue
cytoplasmic granules
(b) Eosinophil:
Bilobed nucleus, red
cytoplasmic granules
Granulocytes
Agranulocytes
(c) Basophil:
Bilobed nucleus,
purplish-black
cytoplasmic granules
(d) Lymphocyte (small):
Large spherical nucleus,
thin rim of pale blue
cytoplasm
(e) Monocyte:
Kidney-shaped nucleus,
abundant pale
blue cytoplasm
Figure 17.10
Leukocytes.
In each case the leukocytes are surrounded by erythrocytes.
Neutrophils, eosinophils, and basophils have visible cytoplasmic granules; lymphocytes and
monocytes do not. (All 1750
3
, Wright’s stain.)
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