Wound healing

Question 1

What are the four main stages of wound healing?

Answer 1

Haemostasis, inflammatory, proliferative, remodelling

Question 2

Function of macrophage in wound healing

Answer 2

Proliferates during inflammatory stage

Question 3

Function of fibroblasts in wound healing

Answer 3

Provides supportive ‘scaffolding’

Question 4

Function of neutrophils in wound healing

Answer 4

Clear away bacteria

Question 5

Function of platelets in wound healing

Answer 5

Clot

Question 6

Function of endothelial cells in wound healing

Answer 6

Revascularise an area with new blood cells

Question 7

Function of fibrin in wound healing

Answer 7

Binds to form clot

Question 8

How long does haemostasis take to occur?

Answer 8

Within seconds to hours after accident

Question 9

Process of haemostasis

Answer 9

Forms fibrin clot so blood doesn’t leak from wound

Vessels rupture, causing platelet aggregation, vasoconstriction and activating the coagulation cascade

Question 10

Process of inflammation

Answer 10

• Cytokines activate vasodilation and attract/activate immune cells to area
• Neutrophils phagocytose bacteria and debris, not important unless wound contaminated
• Macrophages are a source of stimulatory signals and are important for wound healing, phagocytose debris

Question 11

How quickly does inflammation occur?

Answer 11

Hours to days

Question 12

Examples of wound complications

Answer 12

Infection
Adhesion
Keloid (excessive car formation)
Would dehiscence (deficient healing)

Question 13

Ways to heal wound

Answer 13

Sutures/steri-strips
Hyperbaric oxygen chamber 
Manuka honey
Maggots
Wound vac

Question 14

Systematic factors impairing wound healing

Answer 14

Malnutrition
Obesity
Disease
Immunodeficiency
Smoking 
Stress
Steroids 
Old age

Question 15

Local factors impairing wound healing

Answer 15

Pressure
Dehydration
Trauma
Oedema
Infection
Necrosis

Question 16

How quickly does remodelling occur?

Answer 16

Between 3 weeks and a year

Question 17

Process of wound remodelling

Answer 17

• Changes collagen composition over time (type iii to type i)
• Collagen better aligned
• New blood vessels no longer required so removed by apoptosis
• Fibrous scar formed by collagen cross linking increases fibre size

Question 18

Is scar tissue as strong as normal tissue?

Answer 18

No - about 80% as strong

Question 19

What is fibroplasia?

Answer 19

Fibroblasts migrate into wound and are activated by macrophages to replicate, with the dominant cells at the wound edge. They synthesise and deposit collagen and proteoglycans (to hold granulation tissue together)

Question 20

What is epithelialisation?

Answer 20

Epidermal covering reconstituted from wound margin and hair follicle remnants. The keratinocytes migrate across the wound and the neodermis differentiates and stratifies

Question 21

How does contraction occur to pull a wound together?

Answer 21

Fibroblasts differentiate to myofibroblasts that produce contractile proteins to pull the wound edges together

Question 22

Process of proliferation

Answer 22

• Takes days to weeks
• Angiogenesis
• Oxygen required for fibroblasts to make collagen to establish granulation tissue
• Supply of oxygen transported by blood vessels
• New vascularisation is required
• Macrophages and keratinocytes provide angiogenic stimuli
• Start as endothelial cells budding from existing vessels
• Sprout towards wound following oxygen gradient
• Immature vessels differentiate into capillaries/arterioles/venules
• Fibroplasia
• Matrix deposition depends on oxygen and substrate availability and growth factors
• Epithelialisation
• The new epidermal layer is weak as the dermal layer below isn’t yet regenerated
• Contraction: fibroblasts differentiate to myofibroblasts that produce contractile proteins to pull the wound edges together

Question 23

What is a primary wound?

Answer 23

Can be surgical openings

Smooth borders, edges close in vicinity

Question 24

What is a secondary wound?

Answer 24

Large tissue loss, e.g. dog bites

Primary closure not possible