3. Functions of bone
1.
Support and protect the skeletal functions.
2.
Bone stores minerals, especially calcium and
phosphorous, which are mobilized according to the
body needs.
3.
Bone protects the internal organs.
4.
Bone marrow manufactures the blood elements.
5.
Bone remodeling is responsible for the development,
growth, movements, fracture and repair.
5. Osteoprogenitor cell
Location: Present in the deepest layer of periosteum
and lining the vascular canals of compact bone.
Origin: It is mesenchymal in origin.
Function: According to the function needed they divide
by mitosis to give any type of bone cells
Morphology: It resembles mesenchymal cell with pale
stained nucleus and little esinophilic cytoplasm.
7. Bone cells
All types of bone cells are from the same type, the alters
there appearance according to there function: this is what
is called cell modulation.
10. Lamellar bone
a.
Compact bone (ivory bone):
It forms the main part of the shafts of the long bone
and covers the cancellous bone e.g. ribs and flat
bones of the skull.
Its lamellae are arranged in 3 patterns:
n
Circumferential lamellae
n
Havarsian lamellae
n
Interstitial lamellae
13. Lamellar bone
Havarsian lamellae:
n
It is the unite structure of the compact bone and is
called the Haversian system or osteon.
n
The Haversian system if formed of Haversian canal
which is surrounded by (4-20) concentrically
arranged lamellae.
n
The Haversian canal contains B.Vs., nerves, C.T.
and lined by osteoprogenitor cells.
14. Lamellar bone
n
Osteocytes are arranged concentrically in
the osteons (they anastomose with each
others by their process).
n
Haversian canals connected to each others
or to the outer surface or to the bone
marrow spaces with Volkmann's canal.
15. Lamellar bone
Interstitial lamellae:
n
The Haversian systems are separated from each
others by the interstitial lamellae.
n
They represent the remnants of an old resorbed
and remodeled bone.
19. Spongy bone
n
It is present in the central part of the flat bone.
n
It is formed of connected bone trabeculae in the
form of network to give maximum rigidity.
n
In between the bone trabeculae, there are bone
marrow spaces
n
The bone trabeculae have osteocytes.
20.
21. Woven bone
This type of bone is characterized by:
n
Irregular arrangement of the collagen fibers.
n
Great number, large size and irregular arrangement of
the osteocytes.
n
Increase in the organic substance and decrease in the
inorganic contents so; it appears radiolucent in X-ray.
n
This type of bone is resorbed completely and is replaced
by lamellar bone.
22. 3. Bundle Bone
It is referred to the bundles of principal fibers of
either the periosteum or PDL continue into the
bone as sharpeys fibers.
23. Bundle bone
n
It is found adjacent to the periosteum and periodontal
ligament (areas of tension).
n
It is characterized by the presence of the Sharpey's
fibers.
n
It has less number of cells than Woven bone; but more
calcium salts than lamellar bone. So it appears more
radio-opaque and called lamina dura.
n
Its fibers are arranged parallel to the socket wall.
25. Alveolar bone
The alveolar process is that bone containing the alveoli.
It consists of:
n
an outer (lingual and buccal) cortical plate (compact
bone)
n
A central spongiosa (spongous bone) and
n
Alveolar bone (bone lining the alveolus), (bundle
bone)
The alveolar bone and the cortical plate meet at the alveolar
crest (1.5 to 2 mm below the level of CEJ).
28. Alveolar bone
divided into the:
a.
alveolar bone proper
n
lining of the tooth socket or alveolus
n
bone is also called the cribriform plate because of
the many holes through which Volkmann’s canals
pass (from the alveolar bone into the PDL)
29. Alveolar bone
n
also called bundle bone because Sharpey’s fibers insert
into this bone (Sharpey’s fibers = portion of the
fibers of the PDL)
n
these fibers are inserted at a 90 angle into the ABP –
but are fewer in number than those found at the
cemental surface
n
consists of plates of compact bone that surround the
tooth
30. Alveolar bone
n
varies in thickness from 0.1 to 0.5mm
n
can see a portion of the ABP on radiographs lamina
dura
n
most cervical rim = alveolar crest – slightly apical to
the CEJ in healthy patients
31. Alveolar bone
b. supporting alveolar bone
n
has the same components as ABP
n
but is considered to be cortical and trabecular bone –
different arrangement of bony plates
n
cortical bone is made up of cortical plates of compact bone
found on the facial and lingual surfaces
n
plates are usually 1.5 to 3mm thick over the posterior teeth
and can vary over the anterior teeth
33. Alveolar bone
n
alveolar bone can be resorbed with age (edentulous)
n
the underlying basal bone is less affected with age –
because it does not need the presence of teeth to
remain viable
n
loss of teeth + alveolar bone can results in loss in the
vertical dimension of the face – “Popeye” facial
appearance
34. Alveolar bone
n
after tooth extraction the clot is replaced with
immature bone
n
later remodelled as mature secondary bone, very
similar process to fracture repair in skeletal bone
38. Alveolar bone
The alveolar bone is
perforated by many
foramina to allow blood
and nerve supply to the
teeth, so it is referred to
cribriform plate
Hirschfeld
canal
