Bone Flashcards
Functions
Mechanical
- structural
- protective
Physiological
- Ca2+ regulation
- blood cell production in bone marrow
Organic component
35%
Cells
- osteoblasts
- lining cells
- osteocytes
- osteoclasts
Matrix - gives bone flexibility
Inorganic component
65%
Mineral content
- hydroxyapatite
- gives bone strength
Hydroxyapatite - complex salt of calcium and phosphate
Cortical/Compact bone
80%
External surfaces of bone
Walls of diaphyses (shaft)
Principally mechanical function
Cancellous/Trabecular bone
20%
Lattice of fine bone plates
Epiphyses of long bones, vertebral bodies and flat bones
Intercommunicating spaces in mesh filled with bone marrow
Reduces skeletal mass without compromising strength
Density of bone
Cortical - 1700-2000 kg/m3
Lumbar vertebrae - 600-1000 kg/m3
Compressive strength of bone
Femur - 131-224 MPa
Material properties
Properties of the material itself dependent of specimen
Structural properties
Properties of a specific specimen
Difficult to define
Longitudinal growth
Endochondral ossification
Primary ossification centre
Secondary ossification centre (epiphyseal plates)
Ceases when secondary growth plates fuse at adulthood
Circumferential growth
Diameter increases throughout lifespan
Rapid prior to adulthood then very slow
Bone remodelling
Process by which bone mass is maintained, increased or decreased
Continuous repair of micro-damage
Vital process to ensure that bone is fit for purpose
Functional adaptation
Sensory feedback initiates remodelling response
- Osteoclasts —-> bone resorption
- Osteoblasts —-> bone formation
Functional adaptation
Bone atrophy
- inactivity
- bone and mineral content decrease
- predominance of osteoclast
Bone hypertrophy
- increase in activity
- bone mass and mineral content increase
- predominance of osteoblast activity
