CHAPTER 5
Cartilage and Bone
91
Figure 5-9A.
Compact bone.
Ground specimen (un-
stained),
3
68; inset
3
212
A cross section of
compact bone
in a ground specimen (with-
out decalciF
cation of tissue) is shown.
Haversian canals
are
round central spaces in the cross-sectional view; a
Volk-
mann canal
is shown in the longitudinal view. Volkmann
canals run perpendicularly to and connect Haversian canals
with each other (±ig. 5-8). The
inset photomicrograph
shows an
osteon
(
Haversian system
), the basic structural
unit of compact bone, which includes a
Haversian canal
,
lacunae
with housed
osteocytes
, and
concentric lamellae
(±ig. 5-9C). Bone matrices located between the osteons are
called
interstitial lamellae
.
Interstitial
Interstitial
lamellae
lamellae
Concentric
Concentric
lamellae
lamellae
Interstitial
lamellae
Concentric
lamellae
Haversian
Haversian
canals
canals
Lamella
Lamella
Lacuna
Lacuna
Volkmann
Volkmann
canal
canal
Haversian
Haversian
canal
canal
Volkmann
canal
Haversian
canals
Lacuna
Lamella
Haversian
canal
A
lamella
lamella
Haversian
Haversian
canal
canal
Lacuna
Lacuna
Lacuna
Lacuna
Cement line
Cement line
Canaliculi
Canaliculi
Concentric
Concentric
lamellae
lamellae
Interstitial
Interstitial
lamella
Cement line
Haversian
canal
Lacuna
Lacuna
Canaliculi
Concentric
lamellae
Interstitial
B
D. Cui
An osteocyte
within a lacuna
Haversian canal
Canaliculus
Concentric
lamella
Cement line
Lacuna
Canaliculus
C
Figure 5-9B.
Compact bone.
Ground specimen (un-
stained),
3
136; inset
3
388
A higher power view of compact bone in ground specimen
is shown.
Concentric lamellae
and
lacunae
are arranged in
rings, which surround the
Haversian canal
. Each lacuna has
an osteocyte in it. Tiny canals called
canaliculi
contain pro-
cesses of osteocytes and link the lacunae with each other.
The canaliculi permit the osteocytes to communicate via
gap junctions where the processes of adjacent osteocytes
touch each other inside the canaliculi. A
cement line
forms
a boundary between adjacent osteons. Compact bone forms
the hard external portion of bone and provides strong sup-
port and protection.
Figure 5-9C.
A representation of an osteon of the com-
pact bone.
The
osteon
, also called a
Haversian system
, is the basic unit
of the compact bone structure. It has concentrically arranged
laminae (concentric lamellae) surrounding a centrally
located Haversian canal. The Haversian system consists of
(1) a
Haversian canal
through which blood vessels pass, (2)
concentric lamellae
, (3)
lacunae
, each one of which contains
an osteocyte, (4)
canaliculi
, which are small narrow spaces
containing osteocyte processes, and (5) a
cement line
, the
thin dense, external bony layer that surrounds each osteon.
A schematic drawing illustrates an
osteocyte
occupy-
ing a
lacuna
(a space in the bone matrix that houses an
osteocyte) and its thin processes within the canaliculi. The
hairlike processes of the osteocyte are in
contact with the
processes of adjacent osteocytes and provide a means of
communication between
osteocytes.
Types of Bone
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