The physiology of wound healing

Question 1

What are the different aspects to the physiology of wound healing?

Answer 1

Vascular response, inflammatory response, proliferation and maturation. These aspects all overlap

Question 2

What is the vascular response in wound healing?

Answer 2

Trauma results in bleeding -> vasoconstriction for 5-10 minutes -> clotting process -> formation of a fibrin mesh

Question 3

What is the aim of acute vasoconstriction in wound healing?

Answer 3

Reduce blood loss

Question 4

When does the clotting process in wound healing start?

Answer 4

When blood is exposed in the air

Question 5

What do blood and serous fluid do during wound healing?

Answer 5

Cleanse the wound of surface contaminants

Question 6

How do the platelets and fibrin mesh interact in wound healing?

Answer 6

The platelets get trapped in the fibrin mesh and release inflammatory mediators e.g. prostaglandins and histamine

Question 7

What happens to the vessels adjacent to the injury?

Answer 7

Vasodilation and increased permeability

Question 8

How long after injury does vasodilation in the adjacent areas peak?

Answer 8

Twenty minutes

Question 9

What is the role of neutrophils in wound healing?

Answer 9

They release free radicals and proteases and are bactericidal

Question 10

What is the role of macrophages in wound healing?

Answer 10

They ingest dead tissue and release cytokines that recruit lymphocytes and fibroblasts

Question 11

When are lymphocytes released after injury and what do they do?

Answer 11

Enter the wound after 72 hours and secrete chemotactic factors for fibroblasts

Question 12

How long does the inflammatory response last in clean wounds?

Answer 12

Up to 7 days

Question 13

When does the proliferative stage begin?

Answer 13

Two or three days after the event, as the inflammatory response is ending

Question 14

How long does the proliferative stage take?

Answer 14

Can last up to two to four weeks

Question 15

What do fibroblasts secrete during the proliferative stage?

Answer 15

Collagen and glycosmainoglycans

Question 16

What happens during the proliferative stage?

Answer 16

New connective tissue (collagen) fills the wound during this stage - this continues rapidly for 2-3 weeks then it levels off

Question 17

What things during the proliferative stage reduce wound size?

Answer 17

Physiological processes such as granulation (angiogenesis), epithelialisation and contraction reduce wound size

Question 18

When does maturation begin?

Answer 18

Begins approximately when collagen production levels off - usually twenty days after injury

Question 19

How long can maturation last for?

Answer 19

It can last for months or even years, depending on wound size and whether it was initially left open or closed.

Question 20

When does primary intention occur?

Answer 20

Can only be achieved if little or no tissue loss; wound edges need to be directly apposed to each other; results in linear scarring (example: surgical wounds)

Question 21

When does secondary intention occur?

Answer 21

Would edges are not opposed (ulcer); the wound is allowed to granulate - granulation may cause a broader scar (example: pretibial laceration with skin loss)

Question 22

How does secondary intention work?

Answer 22

Epithelialisation occurs from the edge, from hair follicles remnants in the base in the wounds

Question 23

When does tertiary intention work?

Answer 23

Wound is purposely left open (e.g. infection); initially cleaned, debrided and observed; later surgically closed

Question 24

What are general social barriers to healing?

Answer 24

Elderly, diabetes, malnutrition, malignancy, renal or hepatic failure, drugs, immunosuppressive diseases, vitamin deficiencies.

Question 25

What are local factors that are barriers to healing?

Answer 25

Site, infection, oedema, vascular insufficiency, previous radiotherapy