Cartilage
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Specialized connective tissue
Cells: Chondrocytes in lacuna
(chondrogenic cells, chondroblasts)
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Extracellular substance (matrix):
ground substance
collagen fibers, elastic fibers
Features: no blood vessels, lymphatics,
nerves (metabolites exchanged by diffusion)
Covered by perichondrium
(except for fibrocartilage and articular cartilage)
Kinds of cartilage
Hyaline cartilage
• Collagen type II
• trachea, nose, larynx,
articular cartilage of long bone
Elastic cartilage
• Collagen type II
• Elastic fiber
• external ear, epiglottis
Fibrocartilage
• Collagen type I
• intervertebral disc,
pubic symphysis,
articular disc
Hyaline cartilage
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Semitranslucent
The most common cartilage
Perichondrium
outer fibrous layer
inner cellular layer
Chondrogenic cells →
Chondroblast →
Chondrocytes
(appositional growth)
 vascular
Chondrocytes
Matrix
Growing long bone
Articular cartilage:
no perichondrium
IL-1, TNF- → ↑ metalloprotease
↓ collagen and proteoglycans synthesis
osteoarthritis
Hyaline cartilage
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Semitranslucent
The most common cartilage
Perichondrium
Chondrocytes
lacunae
 fat droplets,
 glycogen,
 rER in cytoplasm
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Cell division→
isogenic group
(Interstitial growth)
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Matrix
Hyaline cartilage
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Semitranslucent
The most common cartilage
Perichondrium
Chondrocytes
Matrix
Ground substance
chondroitin sulfate &
collagen fiber
Ground substance: sulfated GAGs (chondroitin,
keratin), and nonsulfated GAGs (hyaluronan)
Protein core,
GAGs
100 chondroitin,
60 keratin
aggrecan
Hyaline cartilage
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Semitranslucent
The most common cartilage
Perichondrium
Chondrocytes
Matrix
Ground substance
chondroitin sulfate &
collagen fiber
 Capsular(pericellular) matrix
 Territorial matrix
 Interterritorial matrix
Amount of sulfated
proteoglycans
Capsular matrix >Territorial >Interterritorial
Age changes:
1. Cell loss, basophilia (proteoglycans ),more matrix,
2. Calcification
bone
3. Asbestos change：fiber bundle, Asbestos
Elastic cartilage
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Perichondrium
Chondrocytes
in lacunae
Matrix:
ground substance
collagen fibers
elastic fibers
orcein
(special staining:
orcein, resorcin fuchsin, Verhoeff‘s hematoxylin)
External ear, Eustachian tube, Epiglottis
elastic cartilage,
elastic fibers
(HE: Verhoeff’s
hematoxylin)
elastic cartilage,
elastic fibers
(stain: elastic van
Gieson)
Elastic fiber : black
collagen fiber : red
Fibrocartilage
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A combination of dense CNT and
hyaline cartilage
No perichondrium: no appositional
growth
Chondrocytes: smaller, arranged in
rows
Matrix :
ground substance ↓,
collagen fibers ↑
Type I &Type II collagen
Distribution:
intervertebral discs,
pubic symphysis,
menisci of the knee
fibroblast
Gomori trichrome staining
Fibrous cartilage
Fibrous cartilage
Development
Mesenchymal cells
(chondrogenic cells)
Chondroblasts
Chondrocytes surrounded
by the cartilageous matrix
Lacuna: small cavities for
chondrocytes
Growing chondrocytes:
basophilic cytoplasm
clear Golgi area
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Growth
Interstitial growth: cell division occurs
within lacunae
Appositional growth: chondrogenic cells
formed new chondroblasts from
perichondrium
perichondrium
chondroblast
Appositional growth
chondrocyte
matrix
Interstitial growth
Kinds of cartilage
Hyaline cartilage Elastic cartilage
Fibrocartilage
Amorphous matrix, type Cartilage matrix, elastic
II collagen fibril
fiber bundles, type II
collagen fibrils
Cartilage matrix,
type I collagen
fiber bundles,
Perichondrium
(appositional growth)
Perichondrium
(appositional growth)
No Perichondrium
Eosin
Orcein stain, resorcin
fuchsin, aldehyde
fuchsin
Light green, eosin
fetal skeleton, trachea,
nose, larynx, articular
cartilgae of long bone
external ear, epiglottis,
larynx
intervertebral disc, pubic
symphysis, articular disc,
insertion of some
tendons and ligaments
Bone Tissue: a specialized CNT
Cells:
 Osteocytes in lacunae,
cell processes in canaliculi
(osteogenic cells, osteoblasts, osteoclasts)
 Matrix
1. Organic substance: bone lamellae (35%)
90% collagen fibers (type I collagen),
ground substance (GAGs glycosaminoglycans,
glycoproteins )
2. Inorganic substance: (65%)
complex calcium phosphate (hydroxyapatite crystals)
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Bone tissue
1. Ground bone section : inorganic structures
(bone lamellae, lacuna,
bone canaliculi)
2. Decalcified bone : Decalcification agents: formic acid, EDTA
organic structures
(periosteum,
collagen fibers,
cells, vessels)
Paraffin section
HE stain
1. Periosteum: covering bone outside
Dense CT, periosteal cells (osteoprogenitor cells)
2. Endosteum: covering bone marrow cavity
endosteal cells (osteoprogenitor cells)
3. Sharpey’s fiber – anchored with bone (tendon or ligament)
Periosteum: Dense CT, periosteal cells
(osteoprogenitor cells)
Masson’s trichrome
P
Architecture of bone
1. Mature compact bone
2. Mature spongy bone (cancellous bone)
Architecture of bone
1. Mature compact bone
2. Mature spongy bone (cancellous bone)
Structure of a compact bone
1. Haversian systems (osteon)
2. Circumferential lamellae
outer & inner
3. Interstitial lamellae
Ground bone section
Haversian system: (osteon)
1.Haversian (central) canal (blood vessels, lymphatics,
nerves)
2.concentric lamellae (4-20 layers) :
3-7 μm thickness/lamella, collagen fibers &
osteocytes (in lacuna)
3. Volkmann’s canal
(blood vessels, nerves)
V
(Volkmann’s canal)
Ground bone section
3. Volkmann’s canal
(blood vessels, nerves)
(Volkmann’s canal)
Decalcified bone section
Cement line
Cement line
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Defined the outer limits of Haversian systems
Collagen-poor, calcified ground substance
Cement line
Architecture of bone
1. Mature compact bone
2. Mature spongy bone (cancellous bone)
Spongy bone (Cancellous bone)
Branching trabeculae & spicules
No haversian system (irregular arrangements of lamellae)
Lacunae & osteocyte
Mature (lamellar)/compact bone
Immature bone
(nonlamellar bone, immature, composed of structural units
the first bone to be produced in called Haversian system (osteon)
a developing fetus):
Growth process
random organization of its
collagen fibers and osteocytes
Immature bone
(woven bone):
nonlamellar organization,
Bundle/woven bone, interlacing
arrangement of collagen fibers,
Hematoxylin stain
Mature (lamellar) bone:
cylindrical Haversian systems,
Eosin stain
decalcified bone cross section
Cellular components of the bone
Osteogenic cells: inner layer of periosteum, endosteum
Osteoblasts : basophilic cytoplasm (rER),
produce osteoid (uncalcified bone matrix)
Bone-lining cells
Osteocytes: surrounded by calcified bone matrix
Osteoclasts: bone resorption
Periosteum: Dense CT, periosteal cells
(Osteoprogenitor cells)
Embryonic Mesenchyme
Spindle-shaped; Pale-staining cytoplasm
P
Masson’s trichrome
Bone-lining cells
Bone remodeling
cease
Flat cells,
Attenuated cytoplasm
Gap junction
Active osteoblasts (basophilic/rER)
Calcified
bone
osteoid
osteoblasts
bone marrow
Bone-lining cells
Bone remodeling
cease
Flat cells,
Attenuated cytoplasm
Gap junction
Osteocyte (in lacuna)
SEM: osteocyte
Decalcified
section
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periosteum,
collagen fibers,
cells,
vessels
H & E stain
Calcified bone
Goldner’s trichrome stain
osteoid
Osteocyte
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Formative osteocyte : active
Quiescent osteocyte : inactive
Resorptive osteocytes
EM of Formative osteocyte EM of quiescent osteocyte
active
osteoid
inactive
osmiophilic lamina :
calcified matrix
Resorptive osteocytes:
• rER, mitochondria, Golgi apparatus,
lysosomes
• no collagen fibrils in pericellular space
• Function: remove bone matrix
(osteocytic osteolysis)
Resorptive osteocyte
active Formative osteocyte
Osteoclast
Large, multinucleated cells, resorbing surfaces
(Howship’s lacunae) of bone 150 μm; 50 nu
Osteoclasts : HE stain
Osteoclasts : Mallory stain
osteoclast
osteoblast
Bone (dark blue)
Calcified cartilage (light blue)
Osteoclasts : Goldner’s trichrome stain
Basolateral
region
Howship’s
lacunae
Clear
zone
Ruffled
border
Extracellullar space: hydrogen ions, collagenase, hydrolytic
enzymes
Ruffled border (leaf-like):
active sites of resorption,
abundant lysosomes (acidophilic),
mitochondria
本次學習重點
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軟骨的基本結構(perichodrium, chondroblasts,
chondrocytes, matrix etc.)及growth patterns
3種軟骨的組織學特徵
硬骨的基本結構
(osteon, osteocyte, osteoblasts, osteoclasts)
(cell size, location, ultrastructure features,
functions)