Lecture 19 - Bones

Question 1

What are the functions of the skeletal systems

Answer 1

• support
• protection from mechanical trauma
• sites of muscle attachment via tendons
• movement
• site of blood cell formation - bone metabolically active [white blood cells]
• fat storage - yellow bone marrow
• calcium and phosphorous reserve - maintain minerals

Question 2

Briefly mention the constituent of bone

Answer 2

• bone is made of cells and extra cellular matrix (ECM). Cells inside the ECM in concentric circles
• there are two types of cells:
  
  • osteoblasts - produces new bone tissues
  • osteoclasts - digests bone tissue
• ECM is made of inorganic matter [50% hydroxyapatite and organic matter 25% collagen matter and the remaining 25% is water]
  note: collagen holds the bone together

Question 3

What is bone remodelling

Answer 3

• the concurrent process of new bone tissue for formation and digestion of existing bone is called bone remodelling
• it helps to reshape bone in response to mechanical loading and also repair bone following fractures
• Calcitonin, dietary Ca2+, mechanical stress, oestrogen in females promote bone formation
• the lack of these and parathyroid hormone promote bone resorption (bone breakdown)

Question 4

List the 2 different types of bone

Answer 4

Compact Bone

• Dense (porosity 5-10%)
• Makes up 80% of total bone weight
• Provides strength yet lightweight

Spongy Bone

• Porosity greater than 70%
• Found in shaft and around surfaces
• Capability to accommodate RBM and YBM

Question 5

indicate on the two stress-strain curves, the type of bone that would show such a response. What is the significance of the two curves (solid line)?

Answer 5

Check pic q10 tut8

Question 6

What is anisotropic material

Answer 6

the bone is an anisotropic material which means it responses to load changes depending on direction of load.

Question 7

Explain bone adaptation

Answer 7

• The playing arm of professional tennis players have cortical thicknesses 35% greater than the opposing arm
• Astronauts experience bone density loss
following space flight (decreased loading)
• Weight lifters develop thickening of the bone at the insertion of active muscles, where stress applied is greatest

Question 8

Describe the 4 ways to injure bone

Answer 8

Tension - bone pulled from different sides, by pulling tendons e.g. marathon running could result in transverse fractures

Compression - likely to occur in fast bowlers for cricket. Landing on a single foot causing hairline fractures. it is an oblique movement

Bending - Likely to occur in football or rugby tackles - this is where the bone bends but does not break. it causes a BUTTERFLY FRACTURE

Torsion - It is twisting of the bone, can happen in any sport that involves changing direction in a short space of time

Question 9

Explain the two types of fracture locations

Answer 9

DIRECT
- injury at the site of force application

INDIRECT (avulsion fractures)
- bone ie pulled out from insertion site by a tendon or a ligament

Question 10

What are 2 bone disorders

Answer 10

Osteo-necrosis - Death of bone cells resutling from cessation of blood flow (interruption in blood flow due to long term steriod use, excessive alcohol intake, radiation therapy

Osteo-porosis - Decrease in bone mineral density - more susceptible to fractures in the bones. Need to ensure enough calcium in diet and Physical activity [functions as a stimulus to maintain or increase bone density]

Question 11

What is needed for overall bone health

Answer 11

• Regular physical activity
• Adequate supply of
  > Calcium
  > Phosphorous
  > Vit C, D, K
• DEXA scans to help show which part of the bones are weaker