MoD - Wound Healing

Question 0

What does regeneration require?

Answer 0

The damage to the tissue to not be extensive and an intact CT scaffold.

Question 1

What is regeneration?

Answer 1

The growth of cells and tissue to replace lost tissue structures

Question 2

What is a labile tissue?

Answer 2

A continuously dividing tissue, one that proliferates through life e.g surface epithelia (GI, skin) and bone marrow

Question 3

What is a stable tissue?

Answer 3

Normally has a low level of replication but can undergo rapid division in response to stimuli. E.e liver, kidney, WBC p, vascular cells (endothelial)

Question 4

What is a permanent tissue?

Answer 4

Cells can’t undergo mitotic division e,g neurones, skeletal and cardiac muscle

Question 5

What is a stem cell?

Answer 5

A precursor cell for many terminally differentiated cells.

When divided one daughter cell remains as a stem cell whilst the other differentiates to a mature non dividing cell.

Question 6

Give an example of a pluripotent cell type?

Answer 6

Haemopoetic cells

Question 7

When does fibrous repair occur?

Answer 7

If the collagen framework of a tissue is destroyed
If there is ongoing chronic inflammation
Or if there is necrosis of specialised parenchymal cells

Question 8

Describe the process of fibrous repair?

Answer 8

Phagocytosis of necrotic tissue debris
Proliferation of endothelial cells (small capillaries grow)
Proliferation of fibroblasts and myofibroblasts
The granulation tissue becomes less vascular and matures into a fibrous scar
Scar matures and shrinks due to contraction of myofibroblasts

Question 9

What is angiogenesis?

Answer 9

The formation of new blood vessels from the proliferation of endothelial cells

Question 10

What is granulation tissue made of?

Answer 10

Fibroblasts (to synthesise collagen), myofibroblasts (wound contraction) endothelial cells (angiogenesis) immune cells (macrophages and neutrophils - for phagocytosis)

Question 11

What do defects in collagen synthesis lead to?

Answer 11

Decreased healing ability

Question 12

What is an autocrine control of fibrous repair?

Answer 12

Cell responds to its own signal

Question 13

What is paracrine control of fibrous repair?

Answer 13

Cell signal acts on an adjacent cell

Question 14

What are growth factors?

Answer 14

Polypeptides that act on specific cell surface receptors considered as ‘local hormones’ can stimulate proliferation or inhibition and cell locomotion.

Question 15

What is epidermal growth factor?

Answer 15

This is produced by inflammatory cells, it is mitogenic for epithelial cells, hepatocytes and fibroblasts
It binds to epidermal growth factor receptors

Question 16

What is vascular endothelial growth factor?

Answer 16

Induces BV development and growth of new vessels in tumours chronic inflammation and wound healing

Question 17

What is platelet derived growth factor?

Answer 17

Stored in platelet a granules and released on activation. Also produced by smooth muscle macrophages and endothelial cells. Causes migration and proliferation of fibroblasts and monocytes.

Question 18

What is tumour necrosis factor?

Answer 18

This induces fibroblast migration, proliferation and collagenase secretion (breaks down collagen)

Question 19

What is contact inhibition?

Answer 19

This is when normal cells replicate until they have cells touching them. Cells adhere to each other by cadherins and adhere to the Extracellular matrix by integrins)

Question 20

When does healing by primary intention occur?

Answer 20

This occurs in incision wounds, closed, clean with opposed edges.
There is only partial destruction of epithelia and CT cells.

Question 21

What are the 6 simple stages of primary intention healing?

Answer 21

1. Haemostasis (scab)
2. Inflammation - neutrophils
3. Macrophages appear- secrete cytokines - attracts cells
4. Granulation tissue invades the space
5. Fibroblasts produce collagen - scar
6. Scar maturation

Question 22

What are the differences in secondary intention healing?

Answer 22

This is seen in wounds with tissue loss and separated edges and in infection. Open wound is filled with granulation tissue. There is a larger clot and more necrotic debris
Inflammatory reaction is more intense
Wound contraction takes place - myofibroblasts
Substantial scar forms

Question 23

Name some local factors affecting wound healing?

Answer 23

Size, location, type of wound
Blood supply
Denervation 
Local infection 
Foreign bodies 
Mechanical stress

Question 24

Name some systemic factors affecting wound healing

Answer 24

Age
Hypoxia 
Obesity 
Diabetes
Malignancy 
Genetic disorders
Drugs (steroids)
Vitamin deficiency

Question 25

What are some of the complications of fibrous repair?

Answer 25

Insufficient fibrosis - breakdown of wound
Excessive fibrosis - scarring, keloids
Disruption of complex tissue - cirrhosis
Excessive contraction - strictures