Muscle Injury: Tissue Healing & Repair (S1)

Question 1

Tissue healing comprises of regeneration and repair. What is the difference between these two things?

Answer 1

• Regeneration = new replacement muscle fibres
• Repair = scar tissue

Question 2

What are the 4 main stages of tissue healing?

Answer 2

1. Bleeding
2. Inflammation
3. Proliferation
4. Remodelling

Question 3

How long does bleeding occur for?

Answer 3

Follows soft tissue injury, can last up to a few hours - depends on nature of tissue and injury.

Question 4

Why do we bleed?

Answer 4

Bleeding is an inflammatory mediator?

Question 5

Inflammation is essential for muscle injury repair. What are the 3 main stages of interactions and reactions?

Answer 5

• Vascular
• Cellular
• Chemical

Question 6

How long does inflammation last?

Answer 6

For up to 1-3 days following bleeding

Question 7

What constitutes the vascular events in the inflammatory response?

Answer 7

• Increased vasodilation + vasopermeability
• Increased flow volume
• Increased exudate
• TISSUE OEDEMA

Question 8

What constitutes the cellular events in the inflammatory response?

Answer 8

• Attraction of phagocytes/neutrophils, monocytes, lymphocytes etc
• Increased phagocytosis
• Phagocytosis of debris -> chemical release

Question 9

What are 4 main possible outcomes of inflammation?

Answer 9

1. Resolution
2. Repair/healing
3. Suppuration/infection
4. Chronic inflammation

Question 10

What stimulates the proliferative phase?

Answer 10

The release of mediators from inflammation

Question 11

What is proliferation?

Answer 11

The generation and deposition of granulation tissue

Question 12

What is the onset of proliferation?

Answer 12

24hrs and then peaks between 2-3 weeks, can occur for months.

Question 13

What are the key events in proliferation?

Answer 13

1. Fibroplasia
2. Angiogenesis
3. Inc in extracellular collagen production
4. Myofibroblasts cause wound contraction to minimize scar
5. Complex interactive response amongst cells + chemical mediators

Question 14

What happens during fibroplasia?

Answer 14

Fibroblasts and endothelial cells migrate into damaged tissue from adjacent areas, they proliferate and increase activity as well as lay down collagen.

Question 15

What is angiogenesis?

Answer 15

The formation of new local circulation, to provide more oxygen and nutrients whilst removing metabolic and repair waste products.

Question 16

What are 3 signs of proliferation?

Answer 16

• Redness - formation of inc no. capillaries
• Swelling - from increased no. capillaries
• Pain - from pressure-sensitive nerve endings

Question 17

What are the key events in remodelling?

Answer 17

1. Orientation of collagen fibres
2. Collagen transition: type I replaced type III collagen
3. Capillaries diminish in number
4. Tensile strength increases

Question 18

How long does remodelling last?

Answer 18

Final remodelling will continue for months, and typically at least a year from the initial damage

Question 19

What are examples of general risk factors known to delay healing?

Answer 19

• Injury history
• Fatigue/Overuse
• Age
• Protein deficiency
• Lower temp
• Medication use (NSAID abuse)
• Mechanical problems
• Disease
• High risk sport/activities

Question 20

What are examples of local risk factors known to delay healing?

Answer 20

• Inadequate nutrition
• Ongoing inflammation
• Drying of the wound
• Excessive movement

Question 21

What is a direct cause of muscle injury?

Answer 21

Trauma (eg sport)

Question 22

What are some indirect causes of muscle injury?

Answer 22

• Fatigue/overuse -> repetetive microdramage exceeds body’s ability to repair eg. shin splints, tennis elbow, compartment syndrome
• Infection
• Ischemia
• Neurological

Question 23

Name some methods of investigation for muscle injury

Answer 23

• MRI
• Diagnostic ultrasound