Chapter 4
Cartilage and Bone
1,Cartilage:
organ=Cartilage tissue+perichondrium
1) structure of cartilage tissue
---cell,chondrocyte
---cartilage matrix
① chondrocyte:
---Structure,LM
embedded in cartilage
lacuna
peripheral cells:
--small and immature
--single and flattened
central cell:
--large and mature,
--round and in group of 2-8 cells
--small and round nucleus
--basophilic cytoplasm
--EM,rich in RER and Golgi complex
*isogenous group,several cells locates
in one lacuna,which are derived from a
single(same) parent cell
② Cartilage matrix
---ground substance:
proteoglycan:
--same to loose CT
--there are more chondroitin sulfate distributed
at the periphery of cartilage lacuna---called as
cartilage capsule(basophilic)
chondronectin
water
---fiber,type and number of fiber depends on the
type of cartilage
2) Classification,according to the fiber
a,Hyaline cartilage,
less collagenous fibril←type II collagen
articular surface,rib cartilage,trachea and
bronchi
b,Fibrous cartilage:
large amount of collagenous fiber bundles
cells are small and less
intervertebral disc,symphysis pubis
c,Elastic cartilage,
large amount of elastic fiber
external ear,epiglottis
3) perichondrium
two layers:
---out layer,contain more fiber-protection
---inner layer,more cells-osteoprogenitor
cell(fusiform in shape)
4) growth of cartilage
---interstitial growth:
inner chondrocyte proliferation→ produce
fiber and matrix.
immature cartilage
---appositional growth:
osteoprogenitor cell→cartilage cell
(chondrocyte) → produce fiber and matrix.
growing and mature cartilage
2.Bone
---consists of bone tissue,periosteum and
endosteum,bone marrow
1) Bone tissue
① Cells:
a,osteoprogenitor cell,stem cell
---structure:
fusiform,small
ovoid nucleus
slight basophilic cytoplasm
exist in periosteum and endosteum
---function,differentiated into osteoblast
and chondrocyte
b,osteoblast:
---structure:
LM:
single layer of
cuboidal or low columnar cell
round nucleus
basophilic cytoplasm
located on the surface of bone tissue
EM:
fine processes
rich in RER,Golgi complex
---function:
ⅰ,synthesize bone collagen fiber and ground
substance-osteoid
ⅱ,release matrix vesicle:
0.1um in diameter
membrane-coated
ALPase(Alkaline phosphatase),ATPase
and pyrophosphatase and phosphoester
(phospholipid)
calcium,crystal of bone salt and calbindin
function,promote calcification
c.osteocyte
---structure:
flattened cell with multiple
long thin processes
located in bone lacuna
and bone canaliculus
basophilic cytoplasm
adjacent cells connect in bone
canaliculus by gap junctions
---function:
Maintain bone matrix
regulate the balance of calcium and
phosphonium
d,osteoclast
---structure,LM:
multinuclear large cell,30-100um
6-50 nuclei
acidophilic cytoplasm
located at peripheral part of bone
EM:
ruffled border-processes
light zone,--under the ruffled border
--microfilament
primary lysosome,pinosome and secondary
lysosome
RER,mito,and Golgi
---function,dissolve and absorb bone matrix
② Bone matrix
---organic matter:
bone collagen fiber -collagenous fiber
(type I collagen)
ground substance:
glycosaminoglycan
glycoproteins:
osteocalcin,involve in calcification of
bone and regulate absorption of bone
osteonectin,related to adherence
between cell and bone matrix,regulate
calcification of bone
osteopontin
---inorganic matter,bone salts
Hydroxyapatite crystal:
Ca10(PO4)6(OH)2
pin-shaped
10-20 nm
longitudinal arranged
*bone lamella,bone matrix arranged in
layers at different direction
2) Architacture of long bone
Long bone is an organ,made up of
bone tissue(shaft and epiphyses),
periosteum and endosteum,bone
marrow
① shaft:
consists of compact bone
a,circumferential lamella:
/outer concentrically-arranged
/inner around inner surface of bone
b,Haversian system (osteon):
/cylindric structure,3-5mm
/central canal,N,BV,CT
/Haversian lamella,4-20 layers
c,interstitial lamella:
/irregular lamella
/remnant of Haversian
or circumferential lamella
*perforating canal:
/transverse canal
/connect with Haversian canal
② epiphyses,composed of spongy bone
---trabeculae:
formed by parallelly-arranged lamella
form a spongy-liked network
---Bone marrow,hemopoietic tissue
③ periosteum and endosteum,CT membrane
---periosteum,DCT
outer layer:more fiber bundles
form perforating fiber
inner layer:
rich in BV,N and osteoprogenitor cells
---endosteum,thin,a layer of osteoprogenitor cell
and CT
---function,provide nutrition and osteoblast for
bone growth and repairing
3) osteogenesis
① basal processes
---formation:
osteoprogenitor cell→ osteoblast → osteoid
↓ ↓calcification
osteocyte + bone matrix
bone tissue
---absorption,osteoclast →dissolve bone
tissue→reconstruction
② basal manner
a,intramembranous ossification:
---CT membrane →osteoprogenitor cell →
osteoblast→ossification center→bone
trabeculae →thicker and longer
---flattened bone and irregular bone formed
in these manner
b,endochondral ossification,e.g,long
bone
ⅰ,formation of cartilage model
Mesenchymal cell→osteoprogenitor cell
→chondroblast→chondrocyte→cartilage
model( consists of hyaline cartilage and
perichondrium)
ⅱ,formation of bone collar
osteoprogenitor cell (perichondrium) →
osteoblast →bone tissue
* These bone tissue surround the central
segment of cartilage model as collar-shaped,
so called bone collar
ⅲ,formation of primary ossification
center and bone marrow cavity
chondrocytes of model center stop
differentiation,enlarge in size,calcification,
dead →CT,BV in periosteum enter
degenerating zone→osteoblast,osteoclast,
osteoprogenitor cell and mesenchymal cell
enter at same time→ossification→primary
ossification center
primary bone marrow cavity(space
between trabeculae) →bone marrow
cavity
ⅳ,Formation of secondary ossification
center and epiphyses
secondary ossification center appears
at the two end of long bone(epiphyses)
epiphyseal plate,cartilage layer
between epiphysis and bone shaft,
growing zone
③ Further growth of bone
---Become longer:
by growth of epiphyseal plate
from epiphyses to shaft,four zones can be seen:
i,reserve cartilage zone,cell is small,round and
basophilic
ii,proliferating cartilage zone,cell is flattened,
isogenous group cell arrange in single line
iii,calcified cartilage zone,cell become large,
mature,round and degenerated,strong
basophilic
iv,ossification zone:
---become thicker,periosteum cell →
osteoprogenitor cell→osteoblast
Cartilage and Bone
1,Cartilage:
organ=Cartilage tissue+perichondrium
1) structure of cartilage tissue
---cell,chondrocyte
---cartilage matrix
① chondrocyte:
---Structure,LM
embedded in cartilage
lacuna
peripheral cells:
--small and immature
--single and flattened
central cell:
--large and mature,
--round and in group of 2-8 cells
--small and round nucleus
--basophilic cytoplasm
--EM,rich in RER and Golgi complex
*isogenous group,several cells locates
in one lacuna,which are derived from a
single(same) parent cell
② Cartilage matrix
---ground substance:
proteoglycan:
--same to loose CT
--there are more chondroitin sulfate distributed
at the periphery of cartilage lacuna---called as
cartilage capsule(basophilic)
chondronectin
water
---fiber,type and number of fiber depends on the
type of cartilage
2) Classification,according to the fiber
a,Hyaline cartilage,
less collagenous fibril←type II collagen
articular surface,rib cartilage,trachea and
bronchi
b,Fibrous cartilage:
large amount of collagenous fiber bundles
cells are small and less
intervertebral disc,symphysis pubis
c,Elastic cartilage,
large amount of elastic fiber
external ear,epiglottis
3) perichondrium
two layers:
---out layer,contain more fiber-protection
---inner layer,more cells-osteoprogenitor
cell(fusiform in shape)
4) growth of cartilage
---interstitial growth:
inner chondrocyte proliferation→ produce
fiber and matrix.
immature cartilage
---appositional growth:
osteoprogenitor cell→cartilage cell
(chondrocyte) → produce fiber and matrix.
growing and mature cartilage
2.Bone
---consists of bone tissue,periosteum and
endosteum,bone marrow
1) Bone tissue
① Cells:
a,osteoprogenitor cell,stem cell
---structure:
fusiform,small
ovoid nucleus
slight basophilic cytoplasm
exist in periosteum and endosteum
---function,differentiated into osteoblast
and chondrocyte
b,osteoblast:
---structure:
LM:
single layer of
cuboidal or low columnar cell
round nucleus
basophilic cytoplasm
located on the surface of bone tissue
EM:
fine processes
rich in RER,Golgi complex
---function:
ⅰ,synthesize bone collagen fiber and ground
substance-osteoid
ⅱ,release matrix vesicle:
0.1um in diameter
membrane-coated
ALPase(Alkaline phosphatase),ATPase
and pyrophosphatase and phosphoester
(phospholipid)
calcium,crystal of bone salt and calbindin
function,promote calcification
c.osteocyte
---structure:
flattened cell with multiple
long thin processes
located in bone lacuna
and bone canaliculus
basophilic cytoplasm
adjacent cells connect in bone
canaliculus by gap junctions
---function:
Maintain bone matrix
regulate the balance of calcium and
phosphonium
d,osteoclast
---structure,LM:
multinuclear large cell,30-100um
6-50 nuclei
acidophilic cytoplasm
located at peripheral part of bone
EM:
ruffled border-processes
light zone,--under the ruffled border
--microfilament
primary lysosome,pinosome and secondary
lysosome
RER,mito,and Golgi
---function,dissolve and absorb bone matrix
② Bone matrix
---organic matter:
bone collagen fiber -collagenous fiber
(type I collagen)
ground substance:
glycosaminoglycan
glycoproteins:
osteocalcin,involve in calcification of
bone and regulate absorption of bone
osteonectin,related to adherence
between cell and bone matrix,regulate
calcification of bone
osteopontin
---inorganic matter,bone salts
Hydroxyapatite crystal:
Ca10(PO4)6(OH)2
pin-shaped
10-20 nm
longitudinal arranged
*bone lamella,bone matrix arranged in
layers at different direction
2) Architacture of long bone
Long bone is an organ,made up of
bone tissue(shaft and epiphyses),
periosteum and endosteum,bone
marrow
① shaft:
consists of compact bone
a,circumferential lamella:
/outer concentrically-arranged
/inner around inner surface of bone
b,Haversian system (osteon):
/cylindric structure,3-5mm
/central canal,N,BV,CT
/Haversian lamella,4-20 layers
c,interstitial lamella:
/irregular lamella
/remnant of Haversian
or circumferential lamella
*perforating canal:
/transverse canal
/connect with Haversian canal
② epiphyses,composed of spongy bone
---trabeculae:
formed by parallelly-arranged lamella
form a spongy-liked network
---Bone marrow,hemopoietic tissue
③ periosteum and endosteum,CT membrane
---periosteum,DCT
outer layer:more fiber bundles
form perforating fiber
inner layer:
rich in BV,N and osteoprogenitor cells
---endosteum,thin,a layer of osteoprogenitor cell
and CT
---function,provide nutrition and osteoblast for
bone growth and repairing
3) osteogenesis
① basal processes
---formation:
osteoprogenitor cell→ osteoblast → osteoid
↓ ↓calcification
osteocyte + bone matrix
bone tissue
---absorption,osteoclast →dissolve bone
tissue→reconstruction
② basal manner
a,intramembranous ossification:
---CT membrane →osteoprogenitor cell →
osteoblast→ossification center→bone
trabeculae →thicker and longer
---flattened bone and irregular bone formed
in these manner
b,endochondral ossification,e.g,long
bone
ⅰ,formation of cartilage model
Mesenchymal cell→osteoprogenitor cell
→chondroblast→chondrocyte→cartilage
model( consists of hyaline cartilage and
perichondrium)
ⅱ,formation of bone collar
osteoprogenitor cell (perichondrium) →
osteoblast →bone tissue
* These bone tissue surround the central
segment of cartilage model as collar-shaped,
so called bone collar
ⅲ,formation of primary ossification
center and bone marrow cavity
chondrocytes of model center stop
differentiation,enlarge in size,calcification,
dead →CT,BV in periosteum enter
degenerating zone→osteoblast,osteoclast,
osteoprogenitor cell and mesenchymal cell
enter at same time→ossification→primary
ossification center
primary bone marrow cavity(space
between trabeculae) →bone marrow
cavity
ⅳ,Formation of secondary ossification
center and epiphyses
secondary ossification center appears
at the two end of long bone(epiphyses)
epiphyseal plate,cartilage layer
between epiphysis and bone shaft,
growing zone
③ Further growth of bone
---Become longer:
by growth of epiphyseal plate
from epiphyses to shaft,four zones can be seen:
i,reserve cartilage zone,cell is small,round and
basophilic
ii,proliferating cartilage zone,cell is flattened,
isogenous group cell arrange in single line
iii,calcified cartilage zone,cell become large,
mature,round and degenerated,strong
basophilic
iv,ossification zone:
---become thicker,periosteum cell →
osteoprogenitor cell→osteoblast
