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Cartilage Functions
Support, model for bone, attachment, protection
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Characteristics of Cartilage
- Avascular! - no blood vessels
- Rigid but not calcified
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Cartilage Components
- Cells:
- -Chondroblasts
- -Chondrocytes - isogenous groups in lacunae
- ECM: covering Perichondrium
- -Collagen (Collagen II)
- -Elastic (+/-)
- -Proteoglycan Matrix: sulfated, binds H2O
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Cartilage Classification
- Hyaline Cartilage
- -support
- -precursor to bone
- -ends of bone: prevents friction
- Elastic Cartilage
- -Flexibility
- -Elastic fibers
- Fibrocartlilage
- -pressure points
- -increased collagen
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Cartilage Growth
•Cartilage enlarges by 2 mechanisms:
–Interstitial growth ~ from within
–Appositional growth ~ from free surface
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Interstitial Growth
- 1. MITOSIS
- 2. ECM PRODUCTION
- 3. CELLS ARE PUSHED APART
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Appositional Growth
Perichondrium has reserve pre-chondroblasts
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Bone Functions
- Mechanical
- -support
- -protection
- -leverage
- Metabolic
- -hematopoesis
- -mineral storage
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Bone Tissue components
- Cells
- -osteocytes
- -osteoblasts
- -osteoclasts: macrophages, derived from blood
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Extracellular Matrix
- •COLLAGEN
- •GROUND SUBSTANCE = OSTEOID
- •MINERALS : Ca++, PO4 -
- - (hydroxyapatite)
- •NOTE: demineralized bone is still bone!
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Classification
- •Shape:
- long
- flat
- irregular
- •Density:
- compact
- spongy
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Bony Tissues -> Bones
- •CT COVERING = PERIOSTEUM
- •SPONGY VS. COMPACT DISTRIBUTION
- •REGIONS OF A LONG BONE:
- –EPIPHYSIS
- •ARTICULAR CARTILAGE
- •EPIPHYSEAL LINE / PLATE
- –DIAPHYSIS
- •NUTRIENT FORAMEN
- –MARROW CAVITY
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Long Bone
- Compact bone - outer
- -periosteum
- Spongy Bone - inner
- -marrow
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Bone
- Compact Bone: Osteons
- Blood Vessels & nerves
- Concentric Lamellae
- Canaliculi
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Compact Bone
- Basic unit
- Osteon= Haversian system
- Bone is vascular !(blood vessels)
- Haversian Canal - runs through bone
- Volkmans Canal - connects haversian canals
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Spongy Bone
- Bone matrix
- Osteocytes
- Osteoblasts
- Osteoclast
- Blood vessels
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Bone Growth
- Mode of bone growth is appositional only!
- Modes of bone formation (during development):
- Intramembranous-
- Mesenchyme->osteoblast->osteocyte->Osteoid->Calcification/Vascularization
Endochondral -
Starts with a cartilage model, all growth in length takes place within cartilage (intersitial growth)
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Bone Growth
- •ELONGATION
- OCCURS VIA INTERSTITIAL GROWTH
- IN EPIPHYSEAL PLATE
•2O CENTER OF OSSIFICATION FORMS
- •EPIPHYSEAL
- PLATE -à LINE (BONE)
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Bone Width
Occurs via appositional growth and continual remodeling
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Bone remodeling
- occurs throughout life
- - hormones, stress, growth, metabolic factors
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Bone Repairs
- •REPAIR OF FRACTURES SIMULATES THE
- EPIPHYSEAL PLATE BY USING A TEMPORARY CARTILAGENOUS SUPPORT
Cartilage Callus may be used as tool for bone elongation or straightening
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