531
CHAPTER FOURTEEN
Blood
Neutrophils
(nu
tro-filz) have fine cytoplasmic gran-
ules that appear light purple with a combination of acid and
base stains. The nucleus of an older neutrophil is lobed and
consists of two to F ve sections (segments, so these cells are
sometimes called
segs
) connected by thin strands of chro-
matin
(f
g. 14.10)
. They are also called
polymorpho-nuclear
leukocytes
(PMNs) due to the variation of nucleus shape
from cell to cell. Younger neutrophils are also called
bands
because their nuclei are C-shaped. Neutrophils are the F rst
white blood cells to arrive at an infection site. These cells
phagocytize bacteria, fungi, and some viruses. Neutrophils
account for 54% to 62% of the leukocytes in a typical blood
sample from an adult.
Eosinophils
(e
o-sin
o-F
lz) contain coarse, uniformly
sized cytoplasmic granules that stain deep red in acid
stain
(f
g. 14.11)
. The nucleus usually has only two lobes
(bilobed). Eosinophils moderate allergic reactions and
defend against parasitic worm infestation. These cells make
up 1% to 3% of the total number of circulating leukocytes.
Basophils
(ba
so-F lz) are similar to eosinophils in size
and in the shape of their nuclei. However, they have fewer,
more irregularly shaped cytoplasmic granules than eosino-
phils, and these granules appear deep blue in basic stain
(f
g. 14.12)
. A basophil’s granules can obscure a view of the
nucleus. Basophils migrate to damaged tissues where they
A typical granulocyte is about twice the size of a red
blood cell. The members of this group include neutrophils,
eosinophils, and basophils. These cells develop in the red
bone marrow in much the same manner as red blood cells.
However, they have a short life span, averaging about twelve
hours.
Polypeptide chain (
2
)
Iron-containing
heme groups
β
Polypeptide chain (
1
)
β
Polypeptide chain (
2
)
(a)
Hemoglobin molecule
(b)
Heme
α
Polypeptide chain (
1
)
α
N
Fe
Fe
+
N
HC
N
NC
H
CH
HC
CH
N
N
H
C
H
NC
H
N
HO
OH
(d)
Bilirubin (C
33
H
36
O
6
N
4
)
NC
H
N
H
C
H
2
N
H
C
H
N
HO
OH
(c)
Biliverdin (C
33
H
34
O
6
N
4
)
FIGURE 14.9
Structural formulas. (
a
) When a hemoglobin
molecule decomposes, (
b
) the heme groups break down into
(
c
) iron (Fe) and biliverdin. (
d
) Most of the biliverdin is then
converted to bilirubin.
TABLE
14.3
|
Major Events in Red Blood
Cell Destruction
1. Squeezing through the capillaries of active tissues damages red
blood cells.
2. Macrophages in the spleen and liver phagocytize damaged red
blood cells.
3. Hemoglobin from the red blood cells is decomposed into heme
and globin.
4. Heme is decomposed into iron and biliverdin.
5. Iron is made available for reuse in the synthesis of new
hemoglobin or is stored in the liver as ferritin.
6. Some biliverdin is converted into bilirubin.
7. Biliverdin and bilirubin are excreted in bile as bile pigments.
8. The globin is broken down into amino acids metabolized by
macrophages or released into the blood.
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