161
CHAPTER FIVE
Tissues
Each central canal contains a blood vessel, so every bone
cell is fairly close to a nutrient supply. In addition, the bone
cells have many cytoplasmic processes that extend outward
and pass through minute tubes in the extracellular matrix
called
canaliculi.
Gap junctions attach these cellular processes
In a bone, the osteocytes and layers of extracellular
matrix, concentrically clustered around a central canal, form
a cylinder-shaped unit called an
osteon,
or a Haversian sys-
tem. Many of these units cemented together form the sub-
stance of bone (see chapter 7, p. 195).
Chondrocyte
Nucleus
Collagenous
fiber
Extracellular
matrix
(a)
(b)
Lacuna
FIGURE 5.25
Fibrocartilage contains many large collagenous f
bers in its extracellular matrix (400×).
Canaliculi
Osteocyte
in lacuna
Central
canal
Lamella
Nucleus
Osteocyte
Cell process in
canaliculus
(a)
(b)
(c)
Osteon
FIGURE 5.26
Bone tissue. (
a
) Bone matrix is deposited in
concentric layers around central canals. (
b
) Micrograph o±
bone tissue (200×). (
c
) Artif
cially colored scanning electron
micrograph o± an osteocyte within a lacuna (6,000×).
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