Wk.1 L3 - Musculoskeletal development from Birth to Adulthood

Question 1

LO

Answer 1

1. Describe brielfy the determinants of childhood growth
2. Explain the concept of mechanobiology
3. Explain growth plate biology and how long bone growth occurs
4. Recall how the joints change with growth
5. Outline the main muscle types and describe skeletal muscle growth
   through post-natal development
6. Describe how bones, joints and muscles respond to mechanical load

[heft] notes summary

Question 2

Determinants of childhood growth rates

Answer 2

• Nutrition
• Hormones
• Genes

Question 3

Mechanobiology

Answer 3

Where Biology meets Physics
- Biological response to physical forces
Strain can be sensed through cell mechano-sensors, fluid flow, comparisson of ECM and excitation signals

Question 4

Post-Natal bone development

Answer 4

Mechanobiology determines shapes of bones

Question 5

Long bone structure

Answer 5

Most have:
* Epiphysis
* Metaphysis
* Diaphysis
* Endosteum
* Periosteum
* Major blood supply
* Marrow cavity

Question 6

Long bone growth

Answer 6

• Endochondral ossification
• Episyses ossify in post-natal development

Question 7

Longitudinal bone growth

Answer 7

Growth plates
1. Chondrocyte proliferation and hypertrophy
1. Hypertrophy and Calcification of cartilage and apoptosis
1. Degradation of transverse septa and vascular invasion.
1. Bone Formation on calcified reminants by osteoblasts

Question 8

Articular Joint Cartilage - Post Natal

Answer 8

• Articular/ Hyaline cartilage in joints is permanent and remains forever
• Articular joint cartilage thickens as bones grtow in response to hormones

Question 9

Articular Joint Cartilage - Changes to Adulthood

Answer 9

Dinstinct Zones form in cartilage layers to withstand and fascilitate mobility
- Thickness increases with chondrocyte volume and accumulation of ECM
1. Superficial Zone
2. Transitional Zone
3. Deep Zone

Question 10

Muscle - Post Natal Development

Answer 10

3 Types form:
Skeletal
Smooth
Cardiac

Question 11

Skeletal Muscle - Pots Natal Development

Answer 11

• Embryonic development determines the number of fibres in each cell muscle
• Post natal growth primarily involves increasing volume of the fibres (hypertrophy)
• Involves the addition of nuclei to growing muscle cells to keep the ratio of nuclei/ cytoplasm balanced

New nuclei are recruited by incorporation of muscle satelite cells into the fibres

Question 12

Bone matrix

Answer 12

Designed to resist load
90%ECM + 10% Water
- 30% Collagen #1
- 60% Hydroxyapetite crystals

Bone tissue = Calcium + Protein

Question 13

Articular Cartilage Response to load

Answer 13

15-20% Proteins (Collagen)
70-80% Water
5-10% Proteoglycans (no minerals)

• Collagen and proteoglycans aggregate in ECM and interstitial fluid to provide resilience to load
• If there is no load on a joint, aptrophy occurs as cartilage maintenance requires load
• Exercise increases chondrocyte production of ECM glycoaminoglycans & decreases ‘matrix-degrading-enzymes’
• Excessive loading (trauma) or aging can cause osteoarthritis

Question 14

Muscle Response to Mechanical load

Answer 14

1-10% ECM CT
~90% fribres

• Fribres respond to load
• Hypertrophy
• New nuclei are recruited
• Prolongued disuse can lead to sarcopenia