92
UNIT 2
Basic Tissues
Figure 5-10A.
Compact bone and cancellous bone,
f nger.
Decalcif
ed bone, H&E,
3
11
Bone has a calcif ed extracellular matrix that is very diFf
-
cult to cut into thin sections. In order to have thin sections
with H&E stain, these bone specimens have to go through
a decalcif cation process that removes calcium compounds
From the specimen. Bone can be classif ed as
compact
bone
(
cortical bone
) and
cancellous bone
(
spongy bone
),
based on its gross appearance.
Compact bone
has a very
high density and a well-organized osteon system (±igs. 5-8
and 5-9A–C). It has no trabeculae and usually Forms the
external aspect oF a bone.
Cancellous bone
(
spongy
bone
)
has a much lower density and contains
bony trabeculae
or
spicules
with intervening
bone marrow
. It usually Forms
the inner part oF a bone, also called
medullary bone
, and is
commonly Found between the inner and the outer tables oF
the skull, at the ends oF long bones (limbs and f ngers), and
in the cores oF other bones.
A
Cancellous
bone
Compact
bone
Bony
trabeculae
Epiphyseal
plate
Articular
cartilage
Bone
marrow
B
Osteocytes
Compact
bone
Endosteum
Endosteum
Periosteum
Osteon
Haversian canal
C
Spongy bone
Spongy
bone
Bony
trabeculae
Bone
marrow space
Hyaline cartilage
Osteocytes
Figure 5-10B.
Compact bone, f
nger.
Decalcif
ed bone,
H&E,
3
105; inset (
left
)
3
154; inset (
right
)
3
127
An example oF
compact bone
From the diaphysis oF the long
bone (f
nger) is shown. The internal surFace is covered by
a single layer oF connective tissue cells Forming the
endos-
teum
. It contains osteoprogenitor cells, which are capable
oF diFFerentiating into osteoblasts. The external surFace is
covered by a thicker layer, the
periosteum
, which contains
blood vessels, nerves, and osteoprogenitor cells. Osteopro-
genitor cells can diFFerentiate into
osteoblasts
, which have
the ability to produce bone matrix,
osteoid
(prebone)
(±ig.
5-11A). Blood vessels branch to supply bone through a
system oF interconnected
Volkmann canals
and
Haversian
canals
(±ig. 5-8).
Osteocytes
are arranged uniFormly in
compact bone. Each osteocyte occupies one lacuna, which
has no isogenous group as it does in cartilage (±ig. 5-9C).
Figure 5-10C.
Cancellous bone (spongy bone), nasal.
Decalcif
ed bone, H&E,
3
34; inset
3
128
Cancellous
bone is also called
spongy bone
. It has a lower
density than compact bone and consists oF
bony trabecu-
lae
, or
spicules
, within a marrow-f
lled cavity. Osteoblasts
line the surFace oF the bony trabeculae. Cancellous bone
displays irregular shapes in the trabecular network.
Bone
marrow
f lls the space between the bony trabeculae (±ig.
5-11A). Most osteocytes in the matrix are arranged in an
irregular pattern rather than in circular rings (±ig. 5-8).
Cancellous bone mainly Forms the inner core oF bone and
provides (1) a meshwork Frame that supports and reduces
the overall weight oF bone and (2) room For blood vessels
to pass through and a place For marrow to Function as a
hemopoietic compartment, housing and producing blood
cells (±ig. 5-11A).
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