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BONE AND CARTILAGELIA DAMAYANTI

Department of Histology - FMUI

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Agenda

Introduction Cartilage

Development of cartilage Growth and repair Components of cartilage Type of Cartilage

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Agenda

Bone Components of bone Development of the bone Microarchitexture of the bone

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Introduction

Cartilage and bone Specialized connective tissue

Cartilage A firm pliable matrix Resist mechanical stress

Bone The hardest tissues of the body Resists stresses place upon it

Comprise the skeleton Function in supporting the body The growth start early in the fetus and continues after birth

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Cartilage

Avascular Regenerate poorly

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Cartilage

Function: subordinate role to bone in support and protection of

the body shock absorber

has the specialized property a highly resilient tissue capable of bearing considering weight having some rigidity giving remarkable flexibility to the body

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Development of cartilage

Developmentbegins at the 5 prenatal weekMesenchyme cells →chondroblast, interlaced

with the connective fibers → deposit extra-cellular matrix → chondrocytes, imprisoned in lacunae

embryonic skeleton → hyaline type Degenerates →replaced by the bone

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Growth

postnatal epiphyseal growth center in long bones articular surface of movable joint open and closedcartilage rings along the larger larger

respiratory passageways Costosternal junctions between ribs and sternum

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Growth

Cartilage An avascular tissue Receive the nutrien by diffusion

through its matrix 2 mechanisms of cartilage growth

Interstitial (endogenous) growth Through mitosis of the imprisoned

chondrocyte Multiple to form a nest cells called as

isogenous cells Expansion of lacunae housing of the

cells Growing of the interstitial matrix

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Growth

Appositional (exogenous) growth Occurs when a cartilage structure increases

in size by new cartilage being deposited on its surface

Dependent on the presence of undifferentiated primitive cells on the surface of the cartilage which differentiate to become chondroblast which lay down new cartilage

Interstitial growth begins earlier cease early in life

Appositional growth throughout life

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Composed by Perichondrium Extra-cellular matrix Cartilage cells

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Perichondrium A connective tissue sheating Compose of

Outer : fibrous layer Inner : cellular layer

Has the blood vessels

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Extracellular matrix Divided into 2 regions

Territorial matrix Surround the lacunae Poor in collagen and rich in

chondroitin sulfate (basophilic and intense staining with Periodic acid-Schiff)

Inter-territorial matrix Bulk of matrix Rich in type II collagen and

poorer in proteoglycans

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Cartilage cells Chondrogenic cells

spindle-shape, narrow cells Cytoplasm is sparse with small golgi apparatus, a few

mitochondria, rough endoplasmic reticulum (RER) and an abundance of free ribosome

differentiate into chondroblast Chondroblast

derived from mesenchyme within the center of chondrofication chondrogenic cells of the inner cellular layers of the

perichondrium

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histology appearance plump, basophilic cells a rich network of RER, a well-developed Golgi complex, numerous

mitochondria Produce and deposit extracellular matrix

Chondrocyte Mature chondroblast surrounded by matrix Entrapped singly or in group in the lacunae near the periphery are ovoid deeper in the cartilage are more rounded

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Cartilage

3 types, based on the fibers present in the matrix Hyaline cartilage Elastic cartilage Fibrocartilage

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Hyaline Cartilage

Fresh state: a bluish-gray, translucent,

glassy, pliable substance the most common cartilage

of the body location

nose, larynx, the ventral ends of ribs, articulating surfaces of movable joints, tracheal rings and bronchi

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Hyaline Cartilage

Matrix Fiber →Collagen fiber

Mostly type II Type IX, X, and XI Not visible under light microscopy

Proteoglycans Aggrecans

Large proteoglycans Composed of protein core

Glycosaminoglycan molecule (chondroitin 4-sulphate, chondroitin-6 sulphate and heparan sulfate) are covalently linked

Link to hyaluronic acid

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Glycosaminoglycan form electrostatic bonds with the collagen

Glycoprotein Large molecule Has binding site for collagen type II, chondroitin-4 and 6 sulfates,

hyaluronic acid and integrin of chondroblast and chondrocyte

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Elastic Cartilage

Fresh state: Yellowish Location→ in few

isolated areaPinna of the ear,

external and internal auditory tubes

Epiglottis Larynx (cuneiform

cartilage)

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Matrix The outer fibrous layer of perichondrium rich in elastic fiber Has abundant fine to coarse branching elastic fibers

interposed with type II collagen fiber bundles Give more flexibility than hyalin cartilage

Less glycogen and lipid accumulation than hyaline cartilage Does not calcify or ossify in old age as does hyaline

cartilage

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Cartilage cells The cells are more closely packed and usually are

found singly in lacunae Chondrocytes more abundant and larger than those

of hyaline cartilage

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Hyaline vs Elastic Cartilage

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Fibrocartilage

Location: Best seen in intervertebral disks Other articular disks: knee, mandible, sternoclavicular

joints For resistance to compression, durability, tensile

strength Develop from dense fibrous tissue richly with

fibroblast Fibroblast with separated matrix differentiate into

chondroblasts→ fibrocartilage

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Fibrocartilage

Has no perichondrium Blends with adjacent connective tissue structure

Matrix Type I collagen fiber Scanty amorphous ground substance

Cells chondrocytes are often aligned in alternating

parallel rows with the thick, coarse bundles of collagen

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Fibrocartilage

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Bone

A specialized connective tissue whose extracellular matrix is calcified, incarcerating the cells that secreted it

the hardest substance of the body Highly vascularized Dynamic tissue Regenerate completely

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Bone

Anatomical appearance Compact bone

Solid, but actually contains microscopic canals and channels

Long bones Femur, tibia, fibulae

Cancellous bone Exists as a latticework or

scaffolding of bone spicules or trabeculae

Usually exists with compact bone Within the shaft of a long bone

and predominates at the ends (epiphyses) of bone

In the flattened bone such as Skull, ribs

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Histological appearancePeriosteum

The layer covered the external surface of bone The cells of bone

Osteogenic (osteoprogenitor) cells Osteoblasts Osteocytes Osteoclasts

The bone matrix

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Periosteum A tough, vascular, fibrous layer Cover the bone except over the

articular surfaces Has 2 layers

The outer layer Largely collagenous fibers and

small component of elastic fibers

The inner (Osteogenic) layer

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The cells of bone Osteoprogenitor cells

Located in the inner cellular layer of periosteum Lining haversian canals Endosteum

Derived from embryonic mesenchyme Can proliferate and differentiate

Osteoblast Chondroblast (low oxygen tension)

Histological appearance Spindle-shape and has a pale staining oval nucleus Scant pale staining cytoplasm

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Osteoblast Derived from osteoprogenitor cells Functions

Synthesis the organic component of the bone matrix

Collagen, proteoglycans, glycoproteins Located at the surface of the bone

Histological appearance In resting state

Flattened or oval in shape Basophilic and flattened nucleus Reddish cytoplasm

In active state cuboidal to columnar cells Basophilic cytoplasm when actively

secreting matrix

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Osteoblast Differentiation Induced by

Hormone Parathyroid hormone

Microenviroment Fibronectin Collagen Procollagen peptides Proteoglycans

Has the receptor for parathyroid hormone on their cell membrane Stimulate osteoblast to secrete osteoclast stimulating factor which activates

osteoclst to resorb bone

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Osteocytes Mature bone cells Derived from osteoblast Housed in the lacunae within the calcified bony matrix Gap junction Histological appearance

The flattened cells Nucleus is flattenned Cytoplasm is poor in organelles

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Osteocytes Mature bone cells Derived from osteoblast Housed in the lacunae within the calcified bony matrix Gap junction Histological appearance

The flattened cells Nucleus is flattenned Cytoplasm is poor in organelles

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Osteoclast The precursor for osteoclast

originates in the bone marrow Has the receptor for osteoclast-

stimulating factor and calcitonin Histological appearance

A large, motile, multinucleated cells Has an acidophilic cytoplasm Occupy the shallow depressions

called as Howship,s lacunae Functions

Resorbing the bone in bone remodelling

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Matrix of the bone Inorganic constituents

Mostly composed by calcium and phosphorus

Magnesium, sodium, potassium, carbonate

Organic constituents Almost exclusively is collagen type I Glysaminoglican, proteoglycan,

glycoprotein Osteocalcin, osteopontin Bone sialoprotein

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Developmental of bone

It always arises from a preexisting tissue which it eventually replaces

2 types Intracartilagenous (endochondral) ossification Intramembraneous (desmal) ossification

Please help yourself for the details

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Intracartilagenous calcification

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The endochondral bone formation at the epiphyseal disk Begins at the center of disk Proceeding toward to the

diaphysis 6 zones

Zone of reserve cartilage Consist of typical hyaline

cartilage cells Zone of proliferating cartilage

Active mitosis among chondrocytes which form parallel stacks of crowded, flattened cells

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Zone of hypertrophy and maturation

Enlargement of chondrocytes which accumulate the glycogen

The matrix is reduced Zone of calcification

The matrix between cells becomes impregnated with calcium and phosphorus and stains basophilic

Zone of degeneration

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Microarchitecture of the bone

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Microarchitecture of the bone

Mature bone Lamellae bone

Lamellae of Havers (Primary lamellae) surrounding the central canal (Canal of Havers)

The osteocytes are sequestered in lacunae located within or between the lamellae

The canal contains nerve fiber, loose connective tissue and flatenned osteogenic cells

The protoplasmic processes of the osteocytes enter the tiny channels that radiate from the lacunae, called as canaliculi to communicate with the adjacent osteocytes

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Microarchitecture of the bone

Canal of Volkmann The canals that communicate one

canal of Havers with the other Penetrate the lamellae to join the

haversian canals where anastomoses of their respective blood vessel occurred

Interstitial lamellae The remnants of older, partially

reabsored haversian system , disrupted during the remodelling of the bone

Outer and inner circumferential lamellae

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Joints

Basic joint components are:1. Bone2. Hyaline Cartilage (articular cartilage): covered the

bone persistently3. Dense collagen tissues (joint supporting tissue) Classification:

SynarthrosisDiarthrosis

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Joint supporting tissues

Mostly dens collagen connective tissues Regenerate fairly good but not as good as bone

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Clinical Correlation

Arthritis Rheumatoid arthritis

Inflammation and swelling of synovial membrane Osteoarthritis

Degeneration of articular cartilage (consequence of old age)

Bursitis Inflammation of bursae

Some large joints communicate with extracapsular, blind-ended sacs, called bursae