Bone 1

Question 1

Bone function (5)

Answer 1

1. support: strong and flexible. Movement (lever through muscle attachments and joints
2. Protection
3. Haematopoesis - RBC, WBC production and maturation
4. Regulation of mineral homeostasis- if not metabolic bone disease e.g. parathyroid hormone
5. Fat sotrage

Question 2

What is Wolf law?

Answer 2

Explains how bone is constantly changing
- Tension and compression cycles create a small electrical potential that stimulated bone deposition and increased density at points of stress

Where stress decreases, bone dec in size/ density- more malleable

Hormones can affect bone density e.g. osteoporosis

Question 3

What are the types of ossification?

where does each occur?

Answer 3

Endrochondral ossification and intramembranous

Intramembranous ossification occurs in flat bones most don’t have a medullary cavity. Relatively rare and most bone formation is endrochondral

Endochondral - long bones= cartilage+BV=bone
occurs at the physics (growth plate)

Question 4

What type of ossification at GP?

• difference between bone modelling and bone remodelling?

Answer 4

endochrondral ossification

Remodelling = replacement of damaged bone. Seen in fracture repair

Modelling = growth (appositional, longitudinal, shape) = the ability for bone the change based on these train put on it

Question 5

Bone structure: types of bone

Answer 5

We have Lamellar bone which consisted of:
- Spongy/ cancellous/ trabecular bone = dissipation of load = metaphysis, flat, cuboidal bones
sit of many primary bone tumours
- compact/ dense/ cortical - diaphysis

and woven (immature bone)

Question 6

What type of ossification at ciboidal bone development?

Answer 6

Intramembranous ossification

Question 7

What stimulated grwoth?

Answer 7

• genetic template
• load (modelling or remodelling
• hormones

Question 8

What is bone modelling?

names of how bone modelling occurs?

Answer 8

Modelling is the ability of bone to change based on the stain put on it
OB form bone
OC remove
work together to alter the shape

Inc size = appositional
Inc length – longitudinal
Alteration in shape = modelling = response to laoding

Question 9

Bone slightly bent. How does modelling change this to become straight?

Answer 9

1. compression force produces greater compression on inside curvature, producing weak electrical currents, stimulating OB
2. overtime bone deposited on inside curve, removed from outside by OC
3. over time bone straightened and final result is the bone matched to the compressive force to which it is exposed

Question 10

What happens if the bone cannot keep up with the compressive load applies?

Answer 10

Stress fractures occur

Question 11

What does anisotropic mean and how does it apply to bone?

Mechanical properties and the 5 forces on bone

Answer 11

ansiotrphic = Behavioural change based on load applied and direction applied
Mechanical properties:
- shape and size of bone
(Cortical thickness, trabecular arrangement
Mineralisation)

• magnitude of load
• direction of laod
• rate of loading

5 forces:
- compression
- tension (pull away)
Bending
Torsion (twisting)
Shearing (bones running against each other obliquely)

Question 12

2 types of bone deformation

Answer 12

Elastic deformation
Bone bends to point, as soon as release It goes back to original state
With loading and unloading, the bone deforms but then returns to the original shape
Stimulates modelling – OC and OB work together to produce bone where wasn’t ebfore

Plastic deformation
With repeated loading and unloading, the bone deforms but does not return to its original shape
Microfractures – pushing into plastic deformation phase, trying to remodel (get rid of diseased bone). If time to heal = ok if not = complete fracture
Cyclic fatigue
Incomplete fractures
Stimulates remodelling

Question 13

6 amrk question

Talk through how a race horse could have a fracture when simply galloping and not lame before

Answer 13

• bone is anisotropic = changes based on load and direction of load applied
• with load bone deforms: elastic (stimulated modelling) and plastic (stimulates remodelling)
• When load is applied to the horses bones i.e from galloping bone deforms
• if continues stress appleid and not enough time for modelling to occur, load appleid can cause micro cracks and so bone to go through elastic deformation to plastic deformation = with loading and unloading it doesn’t return to original shape
• Microcracks stimualted remodelling
• plastic deformation and relativise loading= stress fractures/ micro fractures and not enough time to heal. Won’t be lame
• weakened normal bone
• eventually stress fracture

“stress remodelling” - relativise application of non-supra physiological load
- when bone remodelling cannot keep up with bone damage

Question 14

Most common bones stress fractures in racehorses

Answer 14

MCIII/MTIII condylar fracture
dorsal metacarpal disease
cuboidal bones
tibia
humerus
ilial wing

Question 15

Most common stress fracture in Greyhound

Answer 15

Acetabulum

Central Tarsal Bone

Question 16

Non adaptive remodelling of bone

Answer 16

• stress remodelling

bone reabsorption increasing porosity

Question 17

Homeostasis-

Ca2+ levels too high

Answer 17

Thyroid releases calcitonin = 
increases Ca deposited in bone
decreases Ca uptake in intestines
Decreases Ca reabsorption from urine
Ca falls to normal

Question 18

Homeostasis

Ca2+ too low

Answer 18

Parathyroid releases PTH =
increase Ca2+ released from bone
Increases Ca uptake in intestine
Increases Ca reabsorption from urine