L52: Process of Healing

Question 1

2 types of healing process

Answer 1

Repair (replacement by granulation tissue leading to fibrous tissue)
Regeneration (replacement by similar tissue type, proliferation of undamaged specialised cell)

Question 2

3 types of somatic cells with different inherent regenerative capacities

Answer 2

Labile cells: continue to multiply e.g. epidermis, haemopoietic bone marrow
Stable cells: cease to multiply after growth but retain mitotic ability e.g. Liver and endocrine organs
Permanent cells: lose capacity to proliferate in infancy e.g. nerve cells and myocardium

Question 3

Process of wound healing

Answer 3

1. Regeneration of parenchyma tissue
2. Migration and proliferation
3. Synthesis of extracellular matrix
4. Remodelling
5. Collagenization and acquisition of wound strength

Involved in these steps:

1. Growth factors e.g. fibroblast GF vascular endothelial GF, epidermal GF, IL-1
2. Density dependent regulation of cell growth
3. ECM synthesis and collagenization through fibroblast producing fibrous component (collagen) and ground substances

Question 4

Steps in healing by primary/secondary intention (wound contraction by myofibroblasts)

Answer 4

1. Escape of blood and exudates
2. Scab with clotted blood and fibrin
3. Acute inflammation
4. Basal epithelial cells proliferate and migrate
5. Granulation tissue (fibroblasts + endothelial tissues)
6. Reticulin fibres (collagen fibrils + ground substance)
7. Mature collagen fibre (scar)
8. Loss of vascularity and shrinkage of scar

Question 5

Factors affecting wound healing

Answer 5

1. Local factors (e.g. infection, foreign bodies, blood supply, types of wounding agent)
2. General factors (e.g. nutrition, glucocorticosteroid production, systemic disease)

Question 6

Complications during wound healing

Answer 6

1. Infection
2. Wound dehiscence
3. Implantation (e.g. epidermoid cysts)
4. Excessive granulation tissue / Keloid formation
5. Pigmentations (e.g. haemosiderin)
6. Painful scars (e.g. traumatic neuroma)
7. Weak scars (e.g. incisional hernia)
8. Cicatrisation / late reduction in scar size
9. Neoplasia (e.g. squamous cell carcinoma)

Question 7

Healing of bone fractures

Answer 7

1. Haematoma
2. Inflammation
3. Demolition of detached bone fragments
4. Granulation tissue: ingrowth of capillary and mesenchymal cells from periosteum of cancellous bone (osteogenic potentiality)
5. Callus: osteoblasts —> woven bone; chrondroblast —> cartilagenous tissue
6. Lamellar bone: Osteoblasts lay down osteoid, collagen bundles in orderly lamellar fashion
7. Remodelling

Question 8

Healing in CNS

Answer 8

No regeneration —> fibrosis
Macrophages from microglia and blood monocytes
Glial tissue by astrocytes instead of fibrous tissue

Question 9

Healing in PNS

Answer 9

1. Total degeneration of axon
2. Breakdown of myelin sheath distal to cut (Wallerian degeneration)
3. Transient swelling and breakdown of ER
4. Schwann cell proliferation
5. Axonal sprouts and grow into distal part of nerve

Question 10

Components of granulation tissue

Answer 10

1. Fibroblasts/ myofibroblasts
2. Proliferating endothelial cells
3. Macrophages