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What processes are involved in wound healing

Homeostasis (Prevention of bleeding)
Regeneration OR Repair


What is Regeneration and when is it possible

Regrowth of cells, so that there is minimal evidence of injury

Only possible with minor injuries as an intact collage framework is needed


Compare the types of tissue in regards to proliferative ability

What cell cycle stage are each of them in

Labile: Continuously replicating, In cell cycle

Stable: Normally low level of replication, but can undergo rapid replication if needed, In G0 but can enter G1

Permanent: No replication, have left cell cycle and can’t re-enter


Give 2 examples of each of Labile, Stable, Permanent tissue

Labile: Haematopoietic tissue, Marrow cells

Stable: Bone, Kidneys
Permanent: Cardiac/ Skeletal muscle, Neurons


Define fibrous repair

Replacement of functioning tissue with a scar


What are the steps involved in Scar Formation, how soon do they start
What happens in the first and second one

1. Bleeding and Homeostasis (Secs-mins)
- Severed vessels contract, clot formed
- Scab formation

2. Inflammation (Mins-days)
- Neutrophils appear
- Acute then chronic inflammation

3. Proliferation (Days-weeks)
4. Remodelling (Weeks-years)


What happens in the 3rd step of scar formation (Proliferation)

Granulation tissue invades;

- New capillaries formed by angiogenesis
- Proliferation of Fibro+Myofibroblasts and ECM


What are 3 functions of granulation tissue

Fills the gap
New capillaries supply O2 and nutrients
Contracts to close the gap


What happens in the final step of scar formation (Remodelling)

Maturation of the scar;

- Reduced cell population
- More collagen
- Myofibroblasts contract
- Capillaries disappear


Name the 5 cells involved in Fibrous Repair along with their functions

Neutrophil/ Macrophage: Phagocytosis+ Mediator release
Lymphocyte: Co-ordinate other cells
Endothelial cell: Proliferation + Angiogenesis
Fibroblast: Secrete collagen/ elastin-> ECM
Myofibroblast: Wound contraction


Describe the structure of a fibroblast and myofibroblast

Where can a myofibroblast be found

Spindle shaped nucleus
Cytoplasmic extensions (Hard to see, as they interdigitate)

Myofibroblast: Similar to fibroblast, between a fibroblast and smooth muscle


Name 1 acquired and 3 inherited diseases of defective collagen

Acquired- Scurvy

- Alport Syndrome
- Osteogenesis Imperfecta
- Ehlers-Danlos Syndrome


What is Ehlers-Danlos Syndrome
What are 4 signs

Inherited disorder where collagen fibres lack adequate strength

- Hypermobile joints
- Hyperextensible, Fragile skin
- Poor wound healing
- Colon rupture


What is Alport Syndrome
What are 3 signs

Abnormal type 4 collagen

- Impaired glomerular filtration
- Dysfunction of lens and ear
- Blood in urine as kids/ teens


Name 3 methods of controlling regeneration and repair by cell communication

Direct cell to cell/ stroma contact
Growth factors (Or other local mediators)


What are Growth Factors, how do they work

Name 4

Polypeptides that act on specific cell surface receptors. They cause the cell enter cell cycle and proliferate

- Epidermal growth factor
- Platelet derived growth factor
- Vascular Endothelial growth factor


Describe contact-inhibition
Suggest a condition where this mechanism is defective

Isolated cells replicate until they are in contact with other cells.

This is done via CADHERINS between cells which inhibit further proliferation



In 4 steps, explain healing of skin by Primary Intention

-There is a small wound with apposed edges
- Minimal clotting and granulation tissue formation
- Epidermis regenerates, Dermis repairs (fibrous)
- A small scar remains


In 4 steps, explain healing of skin by Secondary Intention

- There is significant tissue loss, with unapposed edges (Abscess may force edges apart)
- Abdundant clotting/ inflammation/ granulation tissue formation
- Considerable wound contraction is needed

- Epidermis regenerates from edges, Dermis needs significant repair


Compare the 2 classifications of factors affecting wound healing

Local: Relating to wound
Systemic: Relating to individual


Identify 6 LOCAL factors that affect wound healing

Identify 5 SYSTEMIC factors that affect wound healing

1. Size and location of wound
2. Blood supply available
3. Mechanical stress
4. Local infection
5. Foreign body presence
6. Haematoma

1. Age
2. Drugs
3. Malnutrition
4. Anaemia/ Hypoxia/ Hypovolaemia
5. Obesity


Name 6 Complications of Fibrous Repair

- Insufficient fibrosis (Dehiscence)
- Excessive fibrosis
- Fibrous adhesions may be formed
- Loss of function
- Architecture disrupted
- Excessive contraction


Name 4 times Insufficient Fibrosis can occur
Name the scar from excessive fibrosis, who’s at more risk of this
Why are Fibrous Adhesions bad
Why is excessive scar contraction bad

Steroid use (Thinner skin)

A Keloid scar (Made of collagen and elastin); Afro-Caribbeans
Adhesions can cause tube obstruction
Tubes can be constricted


Why does cartilage not heal well

Lacks blood supply, lymphatic drainage and innervation


How do peripheral nerves heal in 2 steps
What is the rate of axon growth

After axon degeneration;

- Proximal axon stumps sprout and elongate
- They used Schwann cells (from degenerated axons) to guide them back to the tissue they innervate

1-3mm a day


What is Gliosis

Describe the 3 stages in the sequence of liver healing

Replacement of neural tissue by proliferation of Glial cells

1. Hepatocyte replicate first
2. Non-parenchymal cells replicate
3. If architecture and hepatocytes damaged severely, cirrhosis occurs