• Cells - maintain extracellular matrix
• Extracellular matrix - framework for support, elasticity, binds water

BONE CELLS
• Osteoblast bone formation
• Osteocyte mature bone cell
• Osteoclast bone resorption
BONE EXTRACELLULAR MATRIX
• collagen and elastin (connective tissue proteins) - tensile strength
• calcium, phosphorous, other ions - compressive strength
• water
BONE CLASSIFICATION
• Long
• Short
• Flat
• Irregular
BONE STRUCTURE
• Cortex, compact
• Cancellous, trabecular
• Periosteum
• Articular cartilage
• Diaphysis
• Metaphysis
• Epiphysis
• Epiphyseal plate
See Bone Structure Picture - 172K

SeeTrabecular Bone Picture - 87K

BONE GROWTH - (another classification system)

• Enchondral ossification - (cartilage growth)
• Intramembranous ossification - (membrane growth)
INTRAUTERINE DEVELOPMENT
• 5th week limb buds, mesenchymal model
• 6th week cartilaginous model
• 7th week cartilage death in diaphysis, osteoblasts, matrix, primary ossification center
• 6th month medullary cavity, 1st epiphysis (distal femoral)
• Remaining epiphyses appear at varying times after birth
See Bone Growth Picture - 48K

ENCHONDRAL OSSIFICATION

• Growth in length
• Epiphyseal plate diaphysis and metaphysis
• Articular cartilage epiphysis
• Cartilage growth - vascularization, calcification and death, replacement by osteoblasts
INTRAMEMBRANOUS OSSIFICATION
• Growth in width
• No cartilage intermediary
• Osteoblasts in deep periosteum
• Osteoclasts in medullary cavity
BONE REMODELING
• Wolff's law
• Continues throughout life
• Bones (and most connective tissues) response to sustained and repetitive by remodeling
BONE FUNCTIONS
• Rigid framework
• Lever system
• Protection
• Cell production, erythrocytes leukocytes and platelets
• Storage, calcium, phosphorous, magnesium and sodium

• Major intercellular component of connective tissues
• Great tensile strength
• "Weave" determines direction and amount of deformation
• weave influenced by motion and forces

ELASTIN

• Intercellular component of connective tissues
• Deforms and regains original state

• Articular (hyaline)
• Collagen and elastin
• Hydrophilic
• Largely avascular (nurtured by diffusion from synovial fluid)
• Resists compression (as long as hydrophilic nature is intact)
• Fibrocartilage
• Mostly collagen
• Thick and dense
• menisci, joint disks
See Articular Cartilage Picture - 89K
 

• Mostly collagen fibers
• Few cells (fibrocytes)
• Collagen fibers parallel to applied forces
• High degree of tensile strength depending on fiber orientation

MUSCLE

• Contractile and noncontractile elements
• Series and parallel arrangement to noncontractile elements