lecture5 cartilage& bone
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CartilageCartilage
BoneBone
PRINCIPAL FUNCTIONS OF PRINCIPAL FUNCTIONS OF CARTILAGECARTILAGE
supporting soft tissuessupporting soft tissues
covering the surfaces of bones covering the surfaces of bones
forming the bone joints forming the bone joints
(shock absorber and sliding area)(shock absorber and sliding area)
development and growth of long development and growth of long
bonesbones
Chondrocytes Chondrocytes
Extracellular matrixExtracellular matrix
GROUND SUBSTANCE GROUND SUBSTANCE
Glicosaminoglicans Glicosaminoglicans
(GAG)(GAG)
Proteoglicans Proteoglicans
hyaluronic acidhyaluronic acid
FIBERSFIBERS
collagen collagen
fibersfibers
elastic fiberselastic fibers
PERICHONDRIUMPERICHONDRIUMThe capsule of connective tissue covering The capsule of connective tissue covering
the cartilagethe cartilage
outer layerouter layer - dense connective tissue - dense connective tissue
collagen type I collagen type I
fibroblastsfibroblasts
the source of nutrients for avascular the source of nutrients for avascular cartilagecartilage
inner layerinner layer
chondroblasts - precursors of chondrocyteschondroblasts - precursors of chondrocytes
TYPES OF CARTILAGETYPES OF CARTILAGEHyaline cartilageHyaline cartilage
the most common formthe most common form
contains mainly collagen type II fiberscontains mainly collagen type II fibers
Elastic cartilageElastic cartilage
many elastic fibers near the collagen type IImany elastic fibers near the collagen type II
more pliable than hyaline cartilagemore pliable than hyaline cartilage
FibrocartilageFibrocartilage
dense network type I collagen fibersdense network type I collagen fibers
present in regions subject to great mechanical present in regions subject to great mechanical stressstress
HYALINE CARTILAGEHYALINE CARTILAGE
articular surfaces of bones forming articular surfaces of bones forming movable jointsmovable jointsthe walls of big respiratory passages the walls of big respiratory passages
larynx, trachea, bigger bronchilarynx, trachea, bigger bronchiepiphyseal plates of long bonesepiphyseal plates of long bonesthe cartilaginous parts of ribsthe cartilaginous parts of ribs
covered by perichondrium covered by perichondrium (except articular cartilage)(except articular cartilage)
HYALINE CARTILAGE HYALINE CARTILAGE CHONDROCYTESCHONDROCYTES
develop from chondroblasts - cells present in develop from chondroblasts - cells present in the inner layer of the perichondriumthe inner layer of the perichondriumat the periphery - elliptic shapeat the periphery - elliptic shapefarther in - become round , form isogenous farther in - become round , form isogenous groupsgroupsisogenous group - develops by mitosis of isogenous group - develops by mitosis of single chondrocyte (5-8 cells in group)single chondrocyte (5-8 cells in group)produce all components of extracellular matrix produce all components of extracellular matrix
well developed RER, Golgi complexwell developed RER, Golgi complex
HYALINE CARTILAGE HYALINE CARTILAGE EXTRACELLULAR MATRIXEXTRACELLULAR MATRIX
collagen type II fibrils embedded in ground collagen type II fibrils embedded in ground substance substance
ground substance :ground substance :
proteoglicans proteoglicans
chondroitin sulfate, keratan sulfatechondroitin sulfate, keratan sulfate
long chains of hyaluronic acidlong chains of hyaluronic acid
chondronectin - glycoprotein providing chondronectin - glycoprotein providing adherence of collagen and chondrocytesadherence of collagen and chondrocytes
water bound to the negative charges of water bound to the negative charges of glicosaminoglicansglicosaminoglicans
Territorial matrixTerritorial matrix
surrounds each chondrocyte of isogenous surrounds each chondrocyte of isogenous groupgroup
rich in proteoglicans poor in collagen fibrilsrich in proteoglicans poor in collagen fibrils
Interterritorial matrixInterterritorial matrix
occurs between isogenous groupsoccurs between isogenous groups
numerous collagen type II fibrilsnumerous collagen type II fibrils
CharacteristicsCharacteristics
firm, resistant to compressionfirm, resistant to compression
ELASTIC CARTILAGEELASTIC CARTILAGE
auricle of the earauricle of the ear
the wall of external auditory canalsthe wall of external auditory canals
auditory tubes (Eustachian tubes )auditory tubes (Eustachian tubes )
epiglottisepiglottis
Presence of perichondriumPresence of perichondrium
ELASTIC CARTILAGEELASTIC CARTILAGEChondrocytes Chondrocytes
similar to cells of hyaline cartilage similar to cells of hyaline cartilage
smaller isogenous groups ( 2- 3 cells)smaller isogenous groups ( 2- 3 cells)
Extracellular matrixExtracellular matrix
abundant network of elastic fibers abundant network of elastic fibers
collagen type II fibrilscollagen type II fibrils
ground substance : the same components ground substance : the same components like in hyaline cartilagelike in hyaline cartilage
FIBROCARTILAGEFIBROCARTILAGE
annulus fibrosus of intervertebral discannulus fibrosus of intervertebral disc
symphysis pubissymphysis pubis
attachments of ligamentsattachments of ligaments
Great resistance to extentionGreat resistance to extention
FIBROCARTILAGEFIBROCARTILAGEChondrocytesChondrocytes
identical to cells of hyaline cartilageidentical to cells of hyaline cartilage
single or in groupssingle or in groups
groups - long raws of chondrocytesgroups - long raws of chondrocytes
Extracellular matrixExtracellular matrix
ground substance - less abundantground substance - less abundant
numerous collagen type I fibers - bundlesnumerous collagen type I fibers - bundles
collagen bundles: collagen bundles:
parallel to raws of cellsparallel to raws of cells
visible in light microscope visible in light microscope
BONEBONESpecific type of connective tissue with Specific type of connective tissue with
calcified extracellular substancecalcified extracellular substance
FunctionsFunctionssupporting soft tissuessupporting soft tissuesprotection of important organsprotection of important organs
CNS in skullCNS in skull thoracic contents in chest thoracic contents in chest
reservoir of calciumreservoir of calcium
OSTEOBLASTSOSTEOBLASTSform a layer which resembles the simple form a layer which resembles the simple epithelium on the surface of boneepithelium on the surface of bone
surround themselves with matrix and become surround themselves with matrix and become ostecytesostecytes
basophilic cytoplasmbasophilic cytoplasm
abundant RER, well developed Golgi complexabundant RER, well developed Golgi complex
Functions:Functions:
synthesize the organic components of matrixsynthesize the organic components of matrix
responsible for calcification of bone matrixresponsible for calcification of bone matrix
play certain role in bone resorptionplay certain role in bone resorption
OSTEOCYTESOSTEOCYTES
develop from osteoblasts which surrounded develop from osteoblasts which surrounded themselves with matrixthemselves with matrix
are located in matrix lacunae are located in matrix lacunae
(one cell per lacuna)(one cell per lacuna)
contact to each other by mean of cytoplasmic contact to each other by mean of cytoplasmic processes existing in canaliculi of matrix processes existing in canaliculi of matrix
surrounded by thin layer of noncalcified matrixsurrounded by thin layer of noncalcified matrix
less RER, smaller Golgi complex condensed less RER, smaller Golgi complex condensed nuclear chromatinnuclear chromatin
Function:Function: maintenance of the matrix maintenance of the matrix
OSTEOBLASTSOSTEOBLASTS OSTEOCYTESOSTEOCYTES
OSTEOCLASTSOSTEOCLASTSlarge, multinuclear cellslarge, multinuclear cellsderive from monocytes derive from monocytes (belong to phagocyte (belong to phagocyte system)system)ruffled border - surface facing ruffled border - surface facing bone ruffledbone ruffledclear zone - adhesion the cell to clear zone - adhesion the cell to the matrixthe matrixacidophilc cytoplasm acidophilc cytoplasm abundant RER and Golgi abundant RER and Golgi complex numerous complex numerous mitochondria and lisosomesmitochondria and lisosomes
Functions:Functions: bone resorption bone resorption bone growth and bone bone growth and bone
remodelingremodeling repair of fracturesrepair of fractures
OSTEOCLASTSOSTEOCLASTS
BONE BONE EXTRACELLULAR MATRIXEXTRACELLULAR MATRIX
Organic componentsOrganic components ( 30-35% of bone weight) ( 30-35% of bone weight)
collagen type I fibers ( 90%)collagen type I fibers ( 90%)
noncollagenous proteins : noncollagenous proteins :
osteonectin, osteocalcin, sialoproteins, osteonectin, osteocalcin, sialoproteins, phosphoproteins, proteolipidsphosphoproteins, proteolipids
proteoglicansproteoglicans
Inorganic componentsInorganic components ( 70% of bone weight) ( 70% of bone weight) calcium phosphate - hydroxyapatyte crystalscalcium phosphate - hydroxyapatyte crystals
PeriosteumPeriosteumLayer of connective tissue covering the boneLayer of connective tissue covering the bone
Outer layerOuter layer - - dense connective tissue dense connective tissue
fibroblastsfibroblasts
numerous collagen fibersnumerous collagen fibers
rich in blood vessels rich in blood vessels (source of vessels for bone)(source of vessels for bone)
Inner layerInner layer
osteoprogenitor cells osteoprogenitor cells (reservoir of osteoblasts)(reservoir of osteoblasts)
EndosteumEndosteum
Thin layer of connective tissue with Thin layer of connective tissue with osteoprogenitor cellsosteoprogenitor cells
Lines internal surfaces of the boneLines internal surfaces of the bone
Types of boneTypes of bone
IMMATURE BONEIMMATURE BONE = = PRIMARY BONEPRIMARY BONE = = = woven bone= woven bone
MATURE BONEMATURE BONE = = SECUNDARY BONESECUNDARY BONE = =
= = lamellar bonelamellar bone Compact boneCompact bone Cancellous bone = spongy boneCancellous bone = spongy bone
SECUNDARY BONE SECUNDARY BONE MATURE BONEMATURE BONE
Present in adultsPresent in adultsCharacteristicsCharacteristics
smaller number of osteocytessmaller number of osteocytesbone matrixbone matrix
abundant, well calcified abundant, well calcified arranged in lamellae arranged in lamellae regular arrangement of collagen fibersregular arrangement of collagen fibers lamellae form osteons (Haversian systems)lamellae form osteons (Haversian systems)
great resistance to mechanical forcesgreat resistance to mechanical forces
SECUNDARY BONE SECUNDARY BONE MATURE BONEMATURE BONE
EndosteumEndosteum
Thin layer of connective tissue with Thin layer of connective tissue with osteoprogenitor cellsosteoprogenitor cells
Lines internal surfaces of the boneLines internal surfaces of the bone
PRIMARY BONE PRIMARY BONE IMMATURE BONEIMMATURE BONE
formed in embryo during bone formationformed in embryo during bone formation
develops in repair process after fracturedevelops in repair process after fracture
replaced by mature bonereplaced by mature bone
irregular array of collagen fibrils in the organic irregular array of collagen fibrils in the organic part of matrixpart of matrix
smaller calcificationsmaller calcification
many osteocytes, little of bone matrixmany osteocytes, little of bone matrix
smaller mechanical resistancesmaller mechanical resistance
HISTOGENESISHISTOGENESIS
Intramembranous ossificationIntramembranous ossification
on the ground of mesenchymal tissueon the ground of mesenchymal tissue
formation of flat bones formation of flat bones
e.g. bones of the skulle.g. bones of the skull
Endochondral ossificationEndochondral ossification
on the ground of cartilaginous model on the ground of cartilaginous model of the boneof the bone
formation of long bonesformation of long bones
INTRAMEMBRANOUS INTRAMEMBRANOUS OSSIFICATIONOSSIFICATION
1. penetration of blood vessels into 1. penetration of blood vessels into mesenchymal tissuemesenchymal tissue
2. mesenchymal cells differentiate into 2. mesenchymal cells differentiate into osteoblastsosteoblasts
3. formation of bone spicules3. formation of bone spicules
ENDOCHONDRAL ENDOCHONDRAL OSSIFICATION OSSIFICATION
1.1.
formation of bone collar within an formation of bone collar within an inner layer of perichondrium of the inner layer of perichondrium of the diaphysisdiaphysis
(intramembranous(intramembranous ossification)ossification)
ENDOCHONDRAL OSSIFICATION
2. 2.
hypertrophy of chondrocyteshypertrophy of chondrocytes
deposition of calcium salts in the deposition of calcium salts in the cartilage matrixcartilage matrix
degeneration of chondrocytes degeneration of chondrocytes
ENDOCHONDRAL ENDOCHONDRAL OSSIFICATIONOSSIFICATION
3. 3.
penetration of osteogenic bud across penetration of osteogenic bud across bone collar into degenerated cartilagebone collar into degenerated cartilage
ENDOCHONDRAL ENDOCHONDRAL OSSIFICATIONOSSIFICATION
4. 4.
phagocytes resorb the cartilagephagocytes resorb the cartilage
osteoblasts start the production of osteoblasts start the production of bone matrix on the remnants of bone matrix on the remnants of cartilagecartilage
PRIMARY OSSIFICATION CENTERPRIMARY OSSIFICATION CENTER
BONE GROWTHBONE GROWTHFLAT BONESFLAT BONES
1. Formation of bone on the external surface 1. Formation of bone on the external surface
osteoprogenitor cells of periosteum osteoprogenitor cells of periosteum (intramembranous ossification)(intramembranous ossification)
2. Resorption of bone on the internal surface2. Resorption of bone on the internal surface
osteoclastsosteoclasts
BONE GROWTH BONE GROWTH LONG BONESLONG BONES
epiphyses - radial growth of cartilage epiphyses - radial growth of cartilage cartilage is gradually replaced by bone cartilage is gradually replaced by bone
the diaphysis increases in width by the diaphysis increases in width by formation of bone by periosteum on the formation of bone by periosteum on the external surfaceexternal surface
diphyseal shaft grows in length as a result diphyseal shaft grows in length as a result of the osteogenic activity of epiphyseal of the osteogenic activity of epiphyseal plate. plate.
BONE AND CALCIUM REGULATORY FACTORS
Somatotrophin(pituitary)
Bone Growth
Calcitonin(parafollicular cellsof thyroid)
CalciumFlux
Parathormone(parathyroid)
Bone Resorption
Osteoclasts Osteocytes“osteocytic osteolysis”
Nutritional Factors:Calcium & Vitamin D DeficiencyChild- RickettsAdult- osteomalaciaVitamin C DeficiencyScurvy- matrix not calicifiable