The document discusses bone structure and function. It defines bone as calcified connective tissue composed of cells and an inorganic matrix. Bone has two main components - cellular components like osteoblasts and osteoclasts, and an inorganic mineral matrix. Bone provides structure, protects organs, stores minerals, and manufactures blood cells. There are two types of bone tissue - lamellar bone which makes up most of the skeleton, and non-lamellar bone which forms more rapidly. Bone remodeling occurs through the balanced actions of osteoblasts which form new bone, and osteoclasts which resorb old bone.

1. • Dr: mahmoud 3mmar
• mobile: 0106 39 700 30
• F.b: m.3mmar9428@yahoo.com
Address: knowledge village center

2. Bone
1)definition.
2)Function.
3)Component.
4)Types.

3. definition
Bone: is specialized C.T (cells , fibers , G.S) with
calcified inercellular substance.

4. Functions of bone
1. Skeletal support of body.
2. Store of Ca , Po4 .
3. Protection of internal organs.
4. Manufacturing of blood elements.

5. component
Tow major component (cellular & matrix)
1. Cellular component: 2 cell lineages
a) osteogenic cells (4)
b) osteoclasts cells
2. Matrix component:
a) 65% mineral
b) 35% matrix (collagen 1,5 & G.s)

6. 1-Osteogenic cells
• Consist of :-
1. Ostoprogenitor cells.
2. Osteoblast.
3. Bone lining cells.
4. Ostocyte.

7. osteocyteBone lining cellsosteoblastosteoprogenitor
OsteoblastFlatened osteoblastCondensing mesenchymeMesenchymal tissueorigin
Surrounded by
bone matrix
mineralized or not
enclosed in lacuna
Extended on bone
surface
On side which will
form new bone
1.Haversian canal
2.Marow space
3.Periostium
4.endosteum
site
‫ــــــــــــــــــــــــــــــــ‬‫ـــــــــــــــــــــــ‬
Apoptosis or encased
in matrix.ostocyte.
Or remain on bone
surface . Bone lining
cells.
Osteoblast at
vascular area.
Condroblast at
avascular area
fate
Through & canaliculi its
its maintain contact with
adjacent osteocyte&B.LC
Large nucleus &
organlles can secrete
protien
•Few synthetic
organelles
jap junction with
ostocyte
.cuboidal or slightly
elongated
.rich in protien
synsthesis& secretory
organelles
Has pale staining
elongated
nucleus
histology
Maintain bone
matrix & can
release Ca ion from
bone matrix
Control mineral
homeostasis &
ensure bone
vitality & its
primary site of ion
exchange beween
Formation on new
bone
Some of them
self renewing
which insure this
cells remain in
postnatal bone
marrow
function

8. 2- osteoclastic cells
1.origin: a) fusion of blood deriving monocyte
b) osteoprogenitor cells in situ
2.site: on bone surface where bone
resorption take place
Occupying howships lacunae

9. 3.histology:
1.Large cells often seen in clusters
2. multinucleated (2:100)
3. rich in acid phosphataze enzyme

10. • Under electron microscope its has
unique chrachterestic which is :
1. Ruffiled border.
2. Clear zone.
3. Vesicular region
4. Basal portion

11. 1. ruffiled border:, its osteoclast cell memb.
forms finger like projection,
adjuacent to bone surface
2.clear zone (seal zone):
1) its the periphery of ruffiled border.
2) its plasma memb. Is opposed closely
to bone surface .
3) adjucent cytoplasm to it is are
devoided from organelles (clear zone)
4) Its riched in actin & talin

12. Functions of clear zone:-
1) attach the cells to mineralized surface.
2) isolate an acid environment between
cells & bone surface.
NB: lamina limitans: its dense matrix layer
between sealing zone & calcified tissue matrix

13. 3.Vesicular region: deep to ruffiled border , its
contains vesicle of various
shapes.
4.basal portion : its portion away from bone
surface consist of many
nuclei each of which is
surrounded by multiple
Golgi complexes ,mitochondria
& R.E.R

16. Bone resorption
Its chemotactic phenomenon since aging
osteocyte may librate some solouble
substance during their degrdation this
substance attract monocyte to target site
that’s will diffrentiate into osteoclast.

17. This done in sequence of conservative events
considered to be as follow:-
1.Attachment:
2.demineralization. (H pump) : cetric , lactic acid chelates
bone by H which increase solubility of bone
3.Degrdation of exposed matrix. (acid Po4 , canthepsin b)
4.endocytosis.
5.transport.

18. Matrix
component
35% organic
65%
inorganic

19. Types of bone
Bone tissue mainly exsist in tow forms
1)Lamellar bone (compact & spongy).
2) Non lamellar bone (woven & bundle).

20. 1.Lamellar bone: this type make up
skeleton & flant bones
its subdivided into 2 types
a) Compact bone.
b) Cancellous bone (spongy).

21. A) Compact bone: is dense like ovary .
form the main part of shaft of
long bones.
represent the external covering
of cancellous bone of ribs , flat bones.

22. Lamellar organization
in the shaft of long bone there are three pattern
of lamellar organization of compact bone.
1) Circumferential or basic lamellae (outer & inner).
2) Haversian lamellae.
3) Interstitial lamellae

26. 1)Circumferential lamellae:
a) outer circumferential lamellae: its
immediately under periosteum , lamellar deposited at
certain number of layers around the circumference of
the shaft.
within & between the lamellae numerous osteocyte with
their process are filling the corresponding lacuna &
canaliculi .
b) Inner circumferential lamellae: its
surround the medullary cavity .
Its has similar arrange ment as outer ine but fewer in
number.

27. 2)Haversian lamellae :betweenn outer &
inner lamellae thre are several groups of
concentric lamellae (5:20) each of which
surrounds canal has diameter 20:300 micron
Its called haversian canal.
Each lamellae has osteocyte concentrically arranged with
their canaliculi radiating toward the central canal.
The inner most canaliculi direct into haversian canal.
Haversian canal contains: B.V , nerves , C.T & lined with
osteoprogenitor cells.

28. Haversian canal run parallel to long axis of shaft of
long bone .
Volkmans canals: its branches from haversian canal
which connect between haversian canals and
ultimately communicate with the surface of bone
outside & medullary cavity inside.
its has the same contents of haversian canal.
Haversian system (osteon): its unit structure
of compact bone & its consist of canal with
surrounding lamellae.

30. 3)Interstitial lamellae: its fragments of
lamenated bone tissue tha are packed between
osteons .
They represent remnants of older , partialy resorbed ,
remolded haversian system

32. 2.Spongy bone (cancellous or trabecular
bone): this type of bone present in :-
1.Epiphysis of long bone.
2.Bony of vertebrate.
3.ribs.
4.Central part of flat bone.

36. Histolgy of bone
Its consist of:
Inter connected network of
bone trabecula with
intervening bone marrow
space
.bone trabecula consist of :
bone lamellae containing
osteocyte.
This trabecula surrounded
by osteoblast

39. What is trabecula ?
Its network of bony
plates or bars or rods
has different
orientation which give
the spongy bon
maximum rigidity
Its also called spicules
which means small
trabecula

40. Blood supply of cancellous bone present
in:
Intervening marrow spaces, consequently
nourishment of oteocyte occurs by
diffusion through canaliculi.

41. Incremental lines of bone (cement lines):-
*Its hypo-mineralized lines than bone matrix
Thus its more ductile than matrix , this can increase
the resistance to fatigue failure of bone.
*This lines are (resting & reversal & faint lines).

42. Faint lineReversal lineResting line
Abrubt change in
direction of
collagen fibers of
each successive
lamellae
They indicate
postosteoclastic activity
occurring on the surface of
the bone
undergoing resorption
(separate between old & new bone)
(bone turn over).
They
demonstrate the
incremental
pattern of bone
formation
(rest of
osteoblast).
cause
Silver impregnationH & EH & EStain
Faint black lineDark blueDark bluecolor
In decalcified
section
In decalcified and ground sectionin decalcified and
ground section
section
‫ــــــــــــــــــــ‬Scalloped linesUndulated linesshape

46. 2. Non lamellar bone its also called:-
1. woven bone .
2. provisional bone .
3. emergency bone .
.its matrix contain more glycosaminoglycan &
glycoprotien than lamellated none and thus less
mineral contents .
. No. of osteocyte in non lamellar bone is more
than that occurs in lamellar bone due to rapid
formation of woven bone.

47. Due to less
inorganic contents
its more
radiolucent in X-
ray than lamellar
bone
And this explain
why bony healed
socket after
extraction cant be
seen in X-ray.

48. Bone of emergency
is finally resorbed
and replaced by
lamellar bone.
It will never change
directly into
lamellar bone.

50. Periostum: its specialized dense C.T covered all bones
of the body except their articular surfaces.
Histologically: its membrane consist of 2 layers, the one
being indistinct from other
1. outer layer (vascular layer).
2. inner layer (osteogenic or cambium layer):
.its attached to bone by sharpey‘s fibers while periostium
itself act as medium for attachment of muscle ,
tendons .
.its provide nutritive fonction to underlying bone & has
osteogenic proprties in young age.
NB: in oral cavity its called muco-periotium.

53. endostium
•Its thin single layer of C.T
like inner layer of
periostium , its lines the
medullary cavity of bones.
•Periosteal surface of
bone more active in
formation of bone than
endosteal one.

54. Oseoid: (osteoid) its layer
of newly deposited
unmineralized bone
matrix that cover
bone surface where
active new bone
formation occurs.
Its 5-10 microne in
thickness
Its type 1 collagen fibrilis which
slightly parallel to bone surface
& proteoglycan and
glycoprotien.

56. Bone development
Bone formation occurs by three mechanisms.
1) endochondral: cartilage is replaced by bone.
(UMC diffrenteate into chndroblasts which lay down
cartilage which later replaced by bone)
2) intramembranous: occurs directly
3) sutural : bone forming along sutural margins

57. Bone turnover: its replacement of old bone by new bon.

58. 1. Osteons of fetal bone replaced by larger, more mature & more lamellar
bone.
2. Leading edge of resorption is called cutting edge.
3. Behind the cutting cone there is a migration of uni-nucleated cells which
differentiate into osteoblast which produce reversal line , thin layer of
phosphoprotien which bind old bone to new bone.
4. On the top of reversal line there are formation of new bone .
5. Area where active formation occurs is termed filling cone.
6. Controlling mechanisms of bone resorption may be genatic or hormonal.
7. Bone remodelling accommodates the growth of bone without losing
function.

59. Bone maturation
mature boneyoung immature
bone
Coarse woven bone
less undulatingless undulatingVery undulatingSurface periostium
lesserlessvery cellularcellularity
more organizedslightly organizeddisorganizedorganization
2ry & 3ry larger
osteons
primary small osteonsnonosteon
little loose C.Tmodrate soft tissue
contents
haigh vascularity &
soft tissue contents
others

60. Thanks
Dr:3mmar