CHAPTER 5
Cartilage and Bone
87
Figure 5-6A.
A representation of ±
brocartilage.
Fibrocartilage
lacks a perichondrium, so no appositional
growth takes place.
Chondrocytes
in
lacunae
are often arranged
in small groups in parallel columns or rows, which correlate
with their method of
interstitial
growth
. The chondrocytes are
smaller and fewer in number in F
brocartilage than in the other
two types of cartilage. Because
type I collagen
±
bers
are pres-
ent in its matrix, the matrix has a dense and coarse appear-
ance. ±ibrocartilage is less fl
exible than the other two types
of cartilage; it provides F
rm support, cushioning, and tensile
strength.
CLINICAL CORRELATION
Figure 5-6C.
Disk Degeneration and Herniation.
Herniation of an intervertebral disk
is a common cause
of pain in the lower back and neck. It is most common
in people in their 30s and 40s. Risk factors include age,
occupation, lifestyle, and genetic propensity.
Degenera-
tion of the intervertebral disk
is because of a combination
of factors that may result in changes in hydration of the
nucleus pulposus
(composed of mucous connective tissue)
and in the strength of collagen, leading to weakening of
the
anulus ±
brosus
(
± brocartilage
). The degenerated disk
nucleus pulposus loses its cushioning ability and exerts
uneven pressure on the surrounding anulus; extrusion of the
nucleus pulposus through the weakened annulus is called
herniation
. It happens most often at the L4–L5 (lumbar)
and L5–S1 (sacral) vertebral levels, causing back pain and
other
neurologic symptoms because of compression of the
nerve roots.
Magnetic resonance imaging is widely used to
visualize the herniated disk. Treatment includes bed rest,
the McKenzie exercise, steroid injections, open discectomy,
and minimally invasive endoscopic discectomy.
A
Nucleus pulposus
T. Yang
T. Yang
C
Normal disk
Extrusion of
nucleus
pulposus
Vertebra
Anulus fibrosus
(fibrocartilage)
D. Cui /T. Yang
Chondrocytes
Type I collagen
Type II collagen
Territorial matrix
Lacuna
A
B
Chondrocytes
Type I
collagen
fibers
Chondrocytes
Figure 5-6B.
Fibrocartilage, intervertebral disk.
H&E,
3
136; inset
3
292
Fibrocartilage
in the intervertebral disk is shown. ±ibrocarti-
lage contains
type II
and
type I collagen
F ber bundles in the
matrix, which makes the matrix look rough, like an oil paint-
ing. Chondrocytes are small and housed in
lacunae
, which are
widely scattered in the matrix. There is no perichondrium asso-
ciated with F
brocartilage; therefore, cartilage growth proceeds
by
interstitial growth
only. ±ibrocartilage has a F rm, dense
matrix, and it can be found in the pubic symphysis, interverte-
bral disks, and insertions of tendons and ligaments.
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