2nd Lecture on Histology of Bone by Dr Mudassar Ali Roomi

8/2/2019 2nd Lecture on Histology of Bone by Dr Mudassar Ali Roomi

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HISTOLOGY OF BONE

BY

DR. MUDASSAR ALI ROOMI (MBBS, M. Phil.)



Bone matrix

• It is the extracellular substance in the bone.

• Composed of inorganic (mineral) and organic

components

•



Bone matrix

INORGANIC (MINERAL)

COMPONENT:• 65 % of the dry weight of the

bone.

• Responsible for hardness of the bone.

• Ca and PO4 are present in theform of hydroxyapatitecrystals.

• Bone – inorganic component =bone looses its rigidity andbecomes as flexible as a

tendon

ORGANIC COMPONENT:

• 35 % of the dry weight of bone.

• Consists of collagen fibers (95% of the organiccomponent)and amorphous

ground substance.• Too much collagen gives

acidophilia to the bone tissue.

• The ground substance:chondroitin SO4 and keratanSO4.

• Bone – organic component =white, brittle and fragile massof bone which breaks easily.



TYPES OF BONE



LOCATION FO COMPACT AND SPONGY BONE

• Epiphysis are composed

of spongy bone and

covered by a thin layer

of compact bone



LOCATION FO COMPACT AND SPONGY BONE

• The flat bones of skull

are composed of two

layers (tables) of

compact boneseparated by a thin

layer of spongy bone.



LOCATION OF COMPACT AND SPONGY BONE

• Shaft (diaphysis) of

long bones consists

almost entirely of

compact bone.• Only a thin layer of

spongy bone lines the

inner surface of the

shaft immediatelysurrounding the

Medullary cavity.



COMPARISON

COMPACT BONE

• Location: In the shaft of long

bones and also in the skull

bones and in the epiphysis.

• Lamellae: arranged to form

Haversian system (osteon).

• Bone marrow: red before

puberty and yellow after

puberty.

• Nature: hard and ivory like

SPONGY BONE(cancellous bone)

• In the epiphysis of long

bones

• Arranged in the form of a

meshwork of bone trabeculae. No

Haversian system

• Red bone marrow.

• spongy



COMPACT BONE

We will discuss it under the following heads:

• It has got a lamellar structure (4 types)

•

Periosteum: outer covering of bone.• Endosteum: inner covering of bone which

lines the medullary cavity.

•

Canals (2 types): Haversian and volkmann’s • Bone cells





Periosteum

• it is the outer most covering of bone.

• It is absent at the articularsurfaces.

• It consists of two layers.

• outer layer of irregularlyarranged dense collagen fibers

• inner cellular layer which lodgesinactive (resting) fibroblastwhich appear as flattened cells.

•Periosteum is pain sensitive

• Sharpy’s fibers: some of thecollagen fibers from theperiosteum penetrate the bonematrix obliquely and bind theperiosteum to bone.



Lamellae of compact bone

1. Periosteal (outercircumferential)lamellae

2. Haversian (concentric)lamellae

3. Interstitial lamellae

4. Inner circumferential

lamellae• Each lamella is 3-7 um

thick.



HAVERSIAN SYSTEM (OSTEON)

• It is the structural unit of the bone tissue.

• It is long cylinder that runapproximately parallel tothe long axis of bone.

• Surrounded by cementsubstance.

• It is composed of :

1. 5-20 concentric lamellae

2. Osteocytes in the lacunae3. Lacunae are located b/w

the successive lamellae.

4. Haversian canal (whichcontains blood vessels,

nerves, and loose C.T.)





Compact bone (t.s)



Compact bone (L.S)



OSTEONS (wow!)



Canaliculi between Osteocytes



Compact bone (t.s)



Compact bone

Identification points:

1. Characteristic lamellae

2. Haversian canal

3. Volkmann’s canal

4. Typical bone cells

5. Haversian system



Spongy bone



Spongy bone

It is idntified by:

1. Trabeculae of the bone

matrix

2. Haemopoitic (bone

marrow) tissue

3. Few Haversian system



COMPARISON BETWEEN

CARTILAGE

• Fibers: Type I and Type II

collagen fibers.

• Vascularity: avascuar• Nerves : absent

• Repair: low

• Communications between

cells: absent

• Hydration: high (75%)

• Mineralization: no

BONE

• Type I collagen fibers.

• Highly vascular.

• Present.

• High

• Gap junctions b/w

osteocytes.

• Low (7%)

• Ca, PO4

2nd Lecture on Histology of Bone by Dr Mudassar Ali Roomi

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