76
UNIT 2
Basic Tissues
CLINICAL CORRELATION
Figure 4-20C.
Marfan Syndrome—Cystic Medial
Degeneration.
Marfan syndrome
is an autosomal dominant
disorder
caused by an
FBN1 gene mutation
, which affects the
formation of elastic F bers, particularly those found in
the aorta, heart, eye, and skin. Signs and symptoms
include tall stature with long limbs and long, thin F n-
gers and enlargement of the base of the aorta accom-
panied by aortic regurgitation. There is increased
probability of dissecting
aortic aneurysms
and pro-
lapse of the mitral valve. Treatment includes pharma-
cologic or surgical intervention to prevent potentially
fatal or long-term complications, but no permanent
cure is yet available. This illustration depicts
cystic
medial degeneration
(
cystic medionecrosis
) of the
aorta, including
disruption
and
fragmentation of
elastic lamellae
in the tunica media of the aorta,
loss
of elastic ± bers,
and
increase in ground substance
causing
formation of cystic space
.
D. Cui
Loss of elastic lamellae and
increased ground substance
Fragmentation of elastic lamellae
Cystic space filled with
amorphous extracellular matrix
C
Figure 4-20A.
Elastic connective tissue, carotid
artery.
Elastic stain (Verhoeff),
3
275; inset
3
516
This is an example of
elastic connective tissue
in the
tunica media of a carotid artery. The wavy
elastic
lamellae
are distributed among collagen and smooth
muscle cells in the tunica media layer of a large artery.
The smooth muscle cells are not visible here because
of the type of stain. In general, the
elastic material
(as
either
elastic ± bers
or
elastic lamellae
) and other con-
nective tissue F
bers are produced by
± broblasts
in the
connective tissue, but in blood vessels,
smooth muscle
cells
are the principal cells that produce
elastic material
and other connective tissue F
bers. Elastic connective
tissue consists predominately of elastic material, and
this allows distension and recoil of the structure. This
tissue can be found in some vertebral ligaments, arte-
rial walls, and in the bronchial tree.
Figure 4-20B.
A representation of elastic
connective
tissue in the tunica media of a large artery.
Thick bundles of
elastic lamellae
are arranged in parallel
wavy sheets, with the
smooth muscle cells
and
collagen
± bers
insinuated between alternating lamellae. The
elas-
tic ± bers
are formed by
elastin
and
± brillin micro±
brils
.
Elastic connective tissue is able to recoil after stretch-
ing. This property in large arteries helps to moderate
the extremes of pressure associated with the cardiac
cycle. Abnormal expression of the
± brillin
(
FBN1
)
gene
is associated with abnormal elastic tissue disease.
Elastic
Elastic
lamellae
lamellae
Elastic
lamellae
Elastic lamellae
Elastic lamellae
Elastic lamellae
A
D. Cui
Ground substance
Collagen fiber
Reticular fiber
Smooth muscle
cell
Elastic lamellae
B
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