CHAPTER 4
Connective Tissue
73
Figure 4-17A.
Loose connective tissue, small
intestine
. H&E,
3
136; inset
3
384
This is an example of the
loose connective tissue
that lies just below the
epithelium
in the lamina
propria of the small intestine. The
collagen f
bers
are loosely arranged and inconspicuous. Many
cells are tightly packed among the F
ber bundles. In
comparison, loose connective tissue has more cells
and fewer F
bers than dense connective tissue. This
type of tissue is well vascularized, fl
exible, and not
highly resistant to mechanical stress.
CLINICAL CORRELATION
Figure 4-17C.
Whipple Disease.
Whipple disease
is a multisystemic disease caused by
an infection of the bacillus
Tropheryma whippleii
. It
primarily affects the small intestine. The clinical symp-
toms include
abdominal pain
,
fl atulence
,
malabsorp-
tion
, and
diarrhea
. Symptoms are varied and depend
upon the organ infected. The lamina propria (loose
connective tissue) of the small intestine reveals an
increased number of
macrophages
. These macrophages
contain large numbers of bacteria within their phago-
somes, which are clearly stained by the PAS stain (peri-
odic acid combined with Schiff reagent). Treatment for
Whipple disease is antibiotic administration, including
intravenous penicillin and streptomycin by mouth.
D. Cui
Lymphocyte
Active
macrophage
Inflammatory
neutrophil
C
Connective
Connective
tissue cells
tissue cells
Collagen
Collagen
fibers
fibers
Loose connective tissue
Loose connective tissue
Epithelial cells
Epithelial cells
Epithelial cells
Loose connective tissue
Collagen
fibers
Connective
tissue cells
A
D. Cui
Plasma cell
Fibroblast
Mast cell
Macrophage
Lymphocyte
Neutrophil
Adipocyte
Collagen fiber
Ground substance
Elastic fiber
B
Figure 4-17B.
A representation o± loose con-
nective tissue
.
There are numerous
connective tissue cells
shown
among F
bers here. They include
f broblasts
,
mac-
rophages
,
adipocytes
,
mast cells
,
plasma cells
, and
leukocytes
. If there is a microorganism invasion
or mechanical trauma, activation of mast cells
and subsequent activation of endothelial cells and
vasodilation are among the responses to the
tissue
injury. Vasodilation promotes delivery of more
blood to the local tissue and leads to increased
local temperature. Loosening of junctions between
endothelial cells enables fl
uid and serum proteins
to leak into the connective tissue. Expression of
adhesive molecules (
selectins
) on endothelial cells
increases the chance that leukocytes can migrate
into the connective tissue from the blood stream.
Mast cells and macrophages also increase in num-
ber to participate in the repair of tissue damage.
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