Ch' 2 Musculoskeletal System

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Ch. 2 Musculoskeletal System

• BASICS
• Std. anatomical posture
• Sagittal plane
• Flexion/Extension
• Medial/Lateral
• Abduction/Adduction
• Radial deviation
• Ulnar deviation
• Pronation/Supination

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SKELETAL SYSTEM

• Rigid links for muscles
• Internal protection
• 200 bones
• Long bones limbs
• Axial bones skull, pelvis

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BONE STRUCTURE - 1

• Cortical/compact
• Cancellous/spongy
• Marrow - blood
• Trabeculae 3D lattice structure
• Wolffs law form follows function

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BONE STRUCTURE - 2

• Cells (2)
• Osteoblasts - form
• Osteocytes - reabsorb
• Extracellular matrix collagen fibers
• Ground substance hydroxy apatite (Ca)
• Lamellar structure
• Canal system

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Ex. 2.1 Bending moments of hollow tubes (bones)
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STRESS-STRAIN CURVES
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COMPACT BONE STRENGTH
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LOADING MODES
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BONE PROPERTIES - 1
Running
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BONE PROPERTIES - 2
Why?
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BONE PROPERTIES - 3

• Daily loading
• Shear fractures
• Bending moments
• Dynamic effects
• Astronauts
• Traction
• Aging

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SOFT CONNECTIVE TISSUE

• Tendons muscle to bone
• Ligaments bone to bone
• Fascia covers organs, skin
• Cartilage articular joints

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FIBERS Collagen, Elastin, Reticulin
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TYPES OF JOINTS

• Fibrous joints connect fixed bones, e.g. skull
• Cartilaginous joints found between
  intervertebral discs
• Articular joints at the articulating (moving)
  end of bones

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ARTICULAR JOINTS

• Synovial capsule surrounds joint
• Synovial fluid, µ0.002
• Meniscus distributes forces
• Poor blood supply
• Poor regeneration

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ARTICULAR (HYALINE) CARTILAGE

• Cells Chondrocytes (2)
• Fibers Collagen (60)
• Ground substance Proteoglycan gel (40)
• Hyaluronic acid water

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ARTICULAR CARTILAGE STRUCTURE 1

• Zonal pattern of cells and fibers parallel,
  random, and perpendicular
• Tidemark transition to bone, anchor

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ARTICULAR CARTILAGE STRUCTURE 2

• Hydrophilic proteoglycan gel
• Movement of water absorb, squeeze out

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ARTICULAR CARTILAGE MECHANICAL PROPERTIES

• Collagen solid elastic
• Proteoglycan liquid viscoelastic

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JOINT LUBRICATION

• Hydrostatic loading forces out fluid
• Hydrodynamic motion causes a wedge effect
• Squeeze-film fluid forced out, moves from high
  to low pressure

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ARTICULAR CARTILAGE MECHANICAL PROPERTIES

• Wear
• Damage to collagen
• Disruption of proeteoglycan gel
• Impairment of interface
• Limited repair, minimal blood flow
• Osteoarthritis secondary inflammation

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CARTILAGINOUS JOINTS

• Between intervertebral discs
• Cartilage end plate
• Annulus fibrosus (A) fibrous outer layer
• Nucleus pulposus (N) gel center
• Dynamic fluid exchange
• Drying, hardening
• Disc herniation