Bone

Question 1

Define long bone

Answer 1

Tubular shape with hollow shaft

Ends expanded for articulations with other bones

Question 2

Define short bone

Answer 2

Cuboidal in shape

Question 3

Define flat bone

Answer 3

Plates of bone (often curved)

Protective function

Question 4

Define irregular bone

Answer 4

Various shapes

Question 5

Define sesamoid bones

Answer 5

Round

Oval nodules in a tendon

Question 6

What are the two bone structures

Macro - visible by eye

Answer 6

Cortical (compact)

Trabecular (cancellous and spongy)

Question 7

Define cortical bone

Answer 7

Compact

Dense, solid

Only spaces are for cells and blood vessels

Question 8

Define trabecular bone

Answer 8

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

Question 9

What are the micro types of bone

Answer 9

Woven bone

Lamellar bone

Question 10

Define woven bone

Answer 10

Made quickly

Disorganised

No clear structure

Question 11

Define lamellar bone

Answer 11

Made slowly

Organised

Layered structure

Question 12

What is the composition of bone - Adult

Answer 12

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

Question 13

How is collagen assembled in bone

Answer 13

In fibrils with mineral crystals situated in ‘gap’ regions between them

Question 14

What does being a composite provide

Answer 14

Collagen - provides elasticity

Mineral - provides stiffness

Question 15

What 4 structures contribute to bone function

Answer 15

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

Question 16

Define modelling

Answer 16

Gross shape is altered

Bone added or taken away

Question 17

Define remodelling

Answer 17

All of the bone is altered

New bone replaces old bone

Question 18

What are the cells of bone

Answer 18

Osteoclast - multinucleated (reabsorbs)

Osteoblast - pump, cuboidal (builders)

Osteocyte - stellate, entombed in bone

Bone lining cell - flattered, lining bone

Question 19

What are the characteristics of osteoblasts

Answer 19

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

Question 20

Characteristics of osteoclasts

Answer 20

Reabsorb bone

Dissolve the mineralised matrix (acid)

Breakdown the collagen in bone (enzymatic)

High expression of TRAP and Cathepsin K

Question 21

7 reasons for bone remodelling

Answer 21

1. Form bone shape
2. Replace woven bone with lamellar bone
3. Reorientate fibrils and trabeculae in favourable direction for mechanical strength
4. Response to loading (exercise)
5. Repair damage
6. Obtain calcium
7. Dysregulated remodelling - disease