Healing

Question 1

Name the stages of wound healing

Answer 1

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

• May progress at different rates
• can overlap
• may have different stages occurring in different areas of same lesion

Question 2

Describe Haemostasis

Answer 2

• Occurs immediately after the injury (unless clotting disorder)
• Vasospasm at time of injury, rapidly subsides- leads to relaxation and further bleeding
• Platelets activated by exposed collagen from damaged vessels
  
  • promote vasoconstriction
  • initiate formation of platelet plug
  • start vessel healing

Question 3

Describe acute inflammation

Answer 3

• fully established by 24 hours after injury
• can last up to 96 hours if disrupted
• cardinal signs observed:
  - redness
  - swelling
  - heat
  - pain
  - loss of function
• Neutrophils and macrophages remove cell debris
  - establish microenvirobment for proliferation (granulation) phase
  - essential for healing

Question 4

Descrive proliferation

Answer 4

-can last 3-4 weeks or longer

• generation of new:
  - Endothelium = angiogenesis
  - Epithelium= epithelialisation
  - Connective tissue stroma = fibroplasia/ desmoplasia

Question 5

Describe remodelling

Answer 5

• Maturation and contraction phase of wound healing
• begins 3-4 weeks after injury (only if earlier stages complete)
• can last 2 years +
• removal of damaged connective tissue
• replacement with new connective tissue

Question 6

Causes of impaired wound healing?

Answer 6

1. Spontaneous causes
   - foreign bodies
   - infections
   - neoplasia
2. Wound specific variables
   - body site
   - vascular supple/ oxygenation
   - mechanical stress
   - desiccation
3. Systemic variables
   - nutrition
   - age
   - sex
   - immobility
   - diseases
4. Exogenous variables
   - medication (cytotoxic drugs, NSAIDs, glucocorticoids)
   - radiation
   - environment

Question 7

Synthesis of ECM?

Answer 7

-Fibroblasts- produce collagen and proteoglycans

Question 8

Describe fibrosis

Answer 8

• fibroblasts align along planes of tissue stress during development
  
  • Langer’s lines (tension lines)
  • Surgical incisions along Langer’s lines reduce postsurgical scar formation

-Feline fibroblasts: responsive to injury (associated with neoplastic transformation)

• fibroblasts and endothelial cells migrate into wounds
  
  • growth factors released during inflammation promote proliferation of fibroblasts and endothelial cells
  • produce EM
  • provisional connective tissue is remodelled into mature matrix

Question 9

What is Granulation tissue?

Answer 9

= distinctive arrangement of connective tissue fibres, fibroblasts and blood vessels

     - fibres and fibroblasts running parallel to wound surface 
     - new vessels running perpendicular to wound surface

Question 10

Appearance of granulation tissue?

Answer 10

• red and granular appearance

- new vessels are leaky and bleed easily

Question 11

Excessive granulation tissue=

Answer 11

proud flesh (hypertrophic scar)

Question 12

Wound contraction?

Answer 12

• Microfibroblasts
  - specialised fibroblasts with contractile activity
  - form in wounds in response to tissue stress
  - contracts the wound to bring edges together

Question 13

Describe Angiogenesis

Answer 13

• Proteolysis of ECM
• Migration and chemotaxis
• Proliferation
• Lumen formation, maturation, and inhibition of growth
• Increased permeability through gaps and trancytosis

Question 14

what does VEGF do?

Answer 14

-makes new blood vessels

Question 15

Will it regenerate, repair or scar?

Answer 15

• depends on cell type (is it post mitotic?)
• depends on extend of injury- is the basement membrane intact?
• where tissue dies = scar
• if you lose basement membrane = scar

Question 16

How does bone heal?

Answer 16

• when a bone fractures, blood vessels break
• get a haematoma
• edges of the bone are separated
• bit at the end is necrotic and needs to be removed
• new vessels and fibroblasts come and lay down fibrous mesh around broken bone to try and stabilise it (still)
• Osteoclasts degrade mineral - release strong chemicals
• new bone formed by osteoblasts everywhere in the callus
• bulge is formed - doesn’t normally disappear completely