Cartilage and Bone
1. Cartilage:
organ=Cartilage tissue+perichondrium
1)
structure of cartilage tissue
Cell
Cartilage
tissue
Chondrocytes
fibers
Extracellular
matrix
Ground substances
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(cell-nests): several
cells locates in one lacuna, which are
derived from a single(same) parent cell
lacuna :area housing the cell.
Their tiny matrix enclosed compartments
are termed lacunae(occupy space).

The deep staining matrix around cell
or cell nests is newly formed and is
called lacunar capsule.
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
articulation surface, rib cartilage, trachea and
bronchi
What is the structure between the chondrocytes
chondrocytes
Extracellular matrix
FCh

The matrix of HC appears fairly
amorphous since the ground
substance and collagen have similar
refractive properties or its intercellular
substance appears to be
homogeneous. We cannot identified
the fiber in the light microscope with
common method stained preparation
of the cartilage.
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
1. Cartilage:
organ=Cartilage tissue+perichondrium
1)
structure of cartilage tissue
Cell
Cartilage
tissue
Chondrocytes
fibers
Extracellular
matrix
Ground substances
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
•Chondrocytes: lacuna area housing the cell

The cells are small present in single
in the Periphery.

Towards the center of a mass of HC,
the chondrocytes are large and are
usually present in groups (of two or
more ),these cells are called cell-nests
(or isogenous cell groups).
What is the structure between the chondrocytes
an amorphous matrix of ground substance
reinforced by collagen fibres
Their tiny matrix enclosed compartments are
termed lacunae. (occupy space)

The deep staining matrix around cell
or cell nests is newly formed and is
called the territorial matrix or lacunar
capsule.
chondrocytes
Extracellular matrix
FCh

The matrix of HC appears fairly
amorphous since the ground
substance and collagen have similar
refractive properties.or its intercellular
substance appears to be
homogeneous. We cannot identified
the fiber in the light microscope with
common method stained preparation
of the cartilage.
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
osteoprogenitor cell
Cells
Elements
of bone
Osteoblast
Osteocyte
Osteoclast
tissue
Extracellular
matrix
Fibers-collagen fibers
Ground substances:
the mineral
Calcium phosphate
Cell
a. osteoprogenitor cell: stem cell
---structure:
 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
canaliculi
lacuna
EM:
 fine prominences
 rich in RER,
 Golgi complex
 mitochondria
---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 prominences
 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
phosphonium
and
d. osteoclast
---structure: LM:

multinuclear large cell, 30-100um

6-50 nuclei

acidophilic cytoplasm

located at peripheral part of bone
EM:
 ruffled border-prominences
 light zone: --under the ruffled border
--microfilament
 primary lysosome, pinosome and secondary
lysosome
 RER, mito. and Golgi
---function: dissolve and absorb bone matrix
Bone matrix
bone collagen fiber -collagenous fiber
(type I collagen)
 ground substance:
glycosaminoglycan

Glycosaminoglycans
Organic constituent Proteoglycans
Chemical
constituents
Fibers and matrix
Calcium
Inorganic constituent
phosphorous
other ions
Osteoid: swollen fibers and matrix, no calcium
Calcification: Calcium salts is deposited in osteoid
---organic matter
glycoproteins: osteocalcin,osteonectin
and osteopontin
---inorganic matter
bone salts: Hydroxyapatite crystal

Ca10(PO4)6(OH)2
10-20 nm
*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
Epiphysis
Diaphysis
Spongy bone and compact bone
•between
adjoining
lamellae we
see small
flattened
spaces or
lacunae
which
contain
osteocytes.
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
①basal processes
---formation:
osteoprogenitor cell→ osteoblast → osteoid
↓
↓calcification
osteocyte + bone matrix
bone tissue
---absorption: osteoclast →dissolve bone
tissue→reconstruction
hyaline cartilage model of that bone is
developed.
②basal 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