Bone Flashcards
Define long bone
Tubular shape with hollow shaft
Ends expanded for articulations with other bones
Define short bone
Cuboidal in shape
Define flat bone
Plates of bone (often curved)
Protective function
Define irregular bone
Various shapes
Define sesamoid bones
Round
Oval nodules in a tendon
What are the two bone structures
Macro - visible by eye
Cortical (compact)
Trabecular (cancellous and spongy)
Define cortical bone
Compact
Dense, solid
Only spaces are for cells and blood vessels
Define trabecular bone
Cancellous
Spongy
Network of bony struts (trabeculae)
Looks like a sponge
Many holes filled with bone marrow
Cells reside in trabeculae and blood vessels in holes
What are the micro types of bone
Woven bone
Lamellar bone
Define woven bone
Made quickly
Disorganised
No clear structure
Define lamellar bone
Made slowly
Organised
Layered structure
What is the composition of bone - Adult
50-70% mineral
- hydroxyapatite - a crystalline form of calcium phosphate
20-40% organic mix
- Collagen (type 1) - 90% of all protein
- Non-collagenous proteins - 10% of all protein
5-10% water
How is collagen assembled in bone
In fibrils with mineral crystals situated in ‘gap’ regions between them
What does being a composite provide
Collagen - provides elasticity
Mineral - provides stiffness
What 4 structures contribute to bone function
Hollow long bone - keeps mass away from neutral axis - minimises deformation
Trabecular bone - gives structural support while minimizing mass
Wide ends - spread load over weak, low friction surface
Flat bone - protective
Define modelling
Gross shape is altered
Bone added or taken away
Define remodelling
All of the bone is altered
New bone replaces old bone
What are the cells of bone
Osteoclast - multinucleated (reabsorbs)
Osteoblast - pump, cuboidal (builders)
Osteocyte - stellate, entombed in bone
Bone lining cell - flattered, lining bone
What are the characteristics of osteoblasts
Form bone (in form of osteoid)
Produce type 1 collagen
High alkaline phosphatase activity
Make non-collagenous proteins
Secrete factors that regulate osteoclasts e.g. RANKL
Characteristics of osteoclasts
Reabsorb bone
Dissolve the mineralised matrix (acid)
Breakdown the collagen in bone (enzymatic)
High expression of TRAP and Cathepsin K
7 reasons for bone remodelling
- Form bone shape
- Replace woven bone with lamellar bone
- Reorientate fibrils and trabeculae in favourable direction for mechanical strength
- Response to loading (exercise)
- Repair damage
- Obtain calcium
- Dysregulated remodelling - disease
