BONE GENERAL HISTOLOGY PRELIM LESSON 5, DENT.pdf

General Histology

1. BONE

2. CONSISTS OF:
•Cells
•Fibers
•Ground substance(extracellular
components are CALCIFIED)
FUNCTIONS:
1. provides for the internal support of the
body
2. provides for the attachment of muscles
and tendons for locomotion

3. 3. protects the vital organs of the cranial and
thoracic cavities
4. encloses the blood forming elements of
the bone marrow
5. plays an important metabolic role as a
mobilizablestore of calcium

4. PHYSICAL PROPERTIES:
1. HIGH TENSILE AND COMPRESSIVE
STRENGTH
2. IT HAS SOME FORM OF ELASTICITY
3. IT IS A RELATIVELY LIGHT WEIGHT
MATERIAL

5. BONE MATRIX –interstitial substance
1.Organic matrix
–consists of collagenous fibers embedded in an
amorphous ground substance; 95% of it is
collagen and the rest are glycoproteins-
chondroitin sulfate, keratansulfate, hyaluronic
acid
* the great toughness and resilience of bone
depend on the organic matrix

6. 2. Inorganic salts (Bone Minerals)
calcium phosphate, citrate ion, carbonate ion,
magnesium, sodium
* hardness of bone depends on its inorganic
constituents
TYPES OF BONE BASED ON ITS HISTOLOGIC
DESIGN:
1. Compact bone
2. Spongy (cancellous) bone

7. COMPACT BONE
-characterized by the
presence of the
HAVERSIAN
SYSTEM or OSTEON
which is made up of
the following
structures:
1. Haversian canal –
contains blood vessel
2. lacuna–contains
the bone cell called
OSTEOCYTE

8. 3. lamella–contains the
bone matrix
4. canaliculi–contains
the cellular processes
of the osteocyte
providing avenues for
the exchange of
metabolites between
the cells and the
perivascular space
5. cement line–marks
the limits of the osteon

9. SPONGY or
CANCELLOUS BONE
1. No Haversian system
2. Has a mosaic of angular
pieces of lamellar bone
(branching bony spicules
or trabeculae with
intercommunicating
spaces occupied by the
bone marrow
3. NOT penetrated by blood
vessels, bone cells are
nourished via
diffusion(food comes
from the endosteal
surface and passes
through the canaliculi

10. BONE PARTS:
macroscopic
1. epiphysis
2.epiphyseal plate
3.metaphysis
4.diaphysis (shaft)
5. medullary or
marrow cavity

12. 1.Epiphyseal plate -made up of cartilage
2.Epiphysis/metaphysis-made up of spongy
bone whose spaces are continuous with the bone
marrow but the outer layer is composed of a thin
layer of compact bone
3.Diaphysis-made up of compact bone
4.Medullary cavity -occupied by the bone marrow
Growth Center:
Epiphyseal plate, Epiphysis, Metaphysis

13. PERIOSTEUM and ENDOSTEUM
Periosteum
-lines the outer surface of the bone
-it is a layer of specialized connective tissue
with osteogenic potency or the ability to form
new bone
Absent at:
1. ends of long bones covered with articular
cartilage
2. sites where tendons and ligaments are
inserted
3. bones formed within tendons or sesamoid
bones
4. subcapsularareas of the neck of the femur
and astragalus

14. Endosteum
-lines the marrow cavities and cavities of
spongy bone
-lined by squamous cells
-has osteogenic potency

15. BONE CELLS
1. OSTEOPROGENITOR CELL
2. OSTEOBLAST
3. OSTEOCYTE
4. OSTEOCLAST

16. GENERAL CHARACTERISTICS:
1. one type may transform into another type
2. believed to be the same cell in different
functional state
CELL MODULATION
-presence of reversible changes in cell appearance

17. OSTEOPROGENITOR CELL
-spindle-shaped
-undifferentiated cell with the capacity for
mitosis and for further structural and
functional specialization
-active during the normal growth of bone
-may be activated during internal
reorganization of bone or in the healing of
fractures and repair of injury becomes an
osteoblast or an osteoclast
-may also develop into an adipose cell,
fibroblast, and hematopoietic cell of the bone
marrow

18. -may also develop into an adipose cell,
fibroblast, and hematopoietic cell of the bone
marrow
-found on or near the free surfaces of bone:
endosteum, periosteum, lining the Haversian
canals, epiphyseal plates

19. OSTEOBLAST
-cuboidal or low columnar with pink granules
-responsible for the formation of bone matrix
-actively engaged in protein synthesis
-found on the advancing surfaces of developing or
growing bones

20. OSTEOCYTES
-flattened body
-principal cells of fully formed bone wherein the
interstitial substance is calcified
-found inside the lacuna
-metabolically inert
-play an active role in the release of calcium from
bone to blood> the process is called OSTEOLYSIS
which is under the control of the parathyroid
hormone
-may modulate to other cell types during bone
resorption

21. OSTEOCLAST
-active agents in bone resorption
-giant cells containing as many as 50 nuclei
-secrete hydrolytic enzyme responsible for
digestion of matrix components [bone resorption]
-its principal source is the fusion of
osteoprogenitorcells
-frequently found in shallow concavities of bone
surface [Howship’slacunae ]

22. *BONE DEVELOPS FROM THE EMBRYONAL
MESENCHYME*
Types of Bone based on its MODE OF
DEVELOPMENT (OSTEOGENESIS )
1. membrane bone
2. cartilage bone

23. MEMBRANE BONES
-flat bones of the skull and part of the
mandible; these bones undergo
INTRAMEMBRANOUS ossification
[ mesenchymal tissue bone ]

24. CARTILAGE BONES
-bones of the extremities, pelvis, vertebral
column; these bones undergo ENDOCHONDRAL
ossification
[ mesenchymal tissue cartilage bone ]

25. INTRAMEMBRANOUS OSSIFICATION:
1. in the primitive tissue (mesenchyme), there
appears a richly vascularized layer of conn.
tissue where cells are in close contact with
one another and the intercellular spaces are
beginning to be filled with collagen fibrils
and a gel-like ground substance
2. then a gradual change in the appearance of
the cells takes place

26. 3. deposition of calcium phosphate occurs and
the cells gradually become imprisoned in the
matrix to become bone cells
4. the fully formed bone appears> in the
COMPACT BONE the trabeculae will thicken
until the spaces are obliterated; in the
SPONGY BONE the thickening of the
trabeculae stops and the intervening vascular
connective tissue is transformed into
HematopoeiticTissue

27. ENDOCHONDRAL OSSIFICATION:
1. ENLARGEMENT OF THE CHONDROCYTES
at the middle of the shaft of the hyaline
cartilage model
2. enlargement of the lacunae at the expense of
the intervening cartilage matrix
3. nests of calcium phosphate crystals begin
to be deposited
4. regressive changes, death, degeneration of
chondrocytes take place

28. 5. osteogenic potencies of cells in the
perichondrium are activated and a thin layer
of bone ( periosteal band or collar ) is
deposited in the midshaft
6. blood vessels will grow in the diaphysis
invading the cavities then will branched out at
either end of the cartilage model
7. cells differentiate into the hematopoietic
elements of the bone marrow and osteoblasts
will congregate on the spicules of the calcified
cartilage matrix and begin to deposit bone
matrix upon them

29. MECHANISM OF CALCIFICATION:
CRYSTALLINE collagen fibers of the matrix
act as nucleation catalyst for transformation
of calcium and phosphate in solution in the
tissue fluids into the solid phase mineral
deposits
CRYSTAL FORMATION: collagen+chondroitin
sulfate + other protein-polysaccharide complex

30. REPAIR OF BONE:
fracture granulation tissue fibrocartilage-
nous callus bony callus ( new bone begins to
form at some distance from the fracture line by
activation of osteoprogenitorcells ) >same
mechanism as in ENDOCHONDRAL
OSSIFICATION>bony union is complete when
the new bone from the two fragments meet

31. GROWTH IN THE LENGTH OF LONG BONES:
as endochondral ossification progresses from
the center of the shaft toward either end of the
cartilage model, the chondrocytes at the
epiphyseal area undergo the same changes but
in a more orderly manner> cells form
themselves into ZONES

32. ZONE OF PROLIFERATION
-occurs at some distance from the
diaphyseo-epiphyseal junction where small
flattened cells undergo division
ZONE OF MATURATION
-cells that are no longer dividing gradually
enlarge

33. ZONE OF HYPERTROPHY OR ZONE OF
PROVISIONAL CALCIFICATION
-cells appear as large vacuolated cells and the
matrix becomes the site of calcium deposition
ZONE OF CELL DEGENERATION
-chondrocytes degenerate, the open ends of
their enlarged lacunae are being invaded by
capillary loops and primitive osteogenic cells
from the marrow spaces of the diaphysis, the
matrix becomes calcified and osteoblasts
proliferate

34. GROWTH IN THE DIAMETER OF LONG
BONE
-this growth is the result of the deposition of
new membrane bone beneath the periosteum
> product of subperiostealintramembranous
ossification
-the deposition of new bone on the outside of
the shaft is accompanied by the appearance of
osteoclasts that erode the inner aspect of the
subperiostealtrabeculae to enlarge the
marrow cavity

35. SURFACE REMODELING OF BONES
-the shape of a bone is maintained during
growth by a continual remodeling of its
surface which will involve bone deposition in
some areas of the periosteum and
absorption in other areas

36. INTERNAL REORGANIZATION OF BONE
-this internal bone destruction and
reconstruction continue actively throughout
life, so at any one time one may see in a bone
cross section:
1. mature osteons( all rebuilding activity has
come to an end)
2. actively forming new osteons
3. absorption cavities being hollowed out in
preparation for new osteons

37. JOINTS AND SYNOVIAL MEMBRANES
-BONES are joined to one another by connective
tissue structures that permit varying degrees of
movement between the adjoining bones
-such structures are called JOINTS or
ARTICULATIONS
-these present extreme variations in character
which depend primarily upon the type of bones
which are joined and varying degrees of motion
permitted by the articulation:

38. 1. immovable joints (skull)
-the connected bones are separated only by a thin
connective tissue layer, the sutural ligament
2. slightly movable (intervertebral
articulations)
-the succeeding vertebrae are joined by dense
fibrous tissue and cartilage
3. freely movable
-here the bones are completely separated by
cartilage and the articular surfaces are surrounded
by fibrous capsule

39. SYNARTHROSES
-joints in which there is little or no movement
TYPES:
1. Synostosis–if the connection between the
bones is of bone
2. Synchondrosis–if it consists of cartilage
3. syndesmosis–if it consists of connective
tissue

40. DIARTHROSES JOINTS
-that permit free movement of the bones
DIARTHRODIAL JOINTS
-there is a cavity and the walls of the joint
cavities are composed of dense connective
tissue whose cells are irregularly distributed
-small amounts of cartilage and all transitions
between the cartilage cells and the joint or
synovial cells can be found
-the articular surface of bones is covered with
hyaline cartilage, where the opposing cartilages
touch, they are not covered with dense
connective tissue but at their bases a small area
of perichondrium is reflectedbackward into the

41. membrane of the joint capsule and at this
point, there are many cartilage cells extending
into the synovial membrane
-articular cartilages contain no blood vessels
and they are nourished by diffusion from the
joint fluid and surrounding tissues

42. LAYERS OF THE JOINT CAPSULE:
1. fibrous layer
–external layer consisting of dense fibrous tissue
2. synovial layer
–inner layer which is more cellular, secretes the
viscid, colorless liquid of the joint cavity (synovial
fluid)