Section 3 Wound healing

1. Definition: Refers to the body’s replacement

of destroyed tissue by living tissue

2. Stages in healing of wound

(1) Escape of blood and exudates

(2) Acute inflammation

(3) Contraction of the wound. The causes of contraction are not known but possible mechanisms are:

①① Shrinkage of scab in superficial woundsShrinkage of scab in superficial wounds

②② Contraction properties of granulation Contraction properties of granulation tissue attributable to contraction of tissue attributable to contraction of myofibroblasts or tissue re-modeling. myofibroblasts or tissue re-modeling.

(4) Proliferation and migration of fibroblasts and endothelial cells.

(5) Progressive increase in mature collagen fibres during the second week forming a scar.

(6) Loss vascularity and shrinkage of the scar.

3. Type of wound healing

(1) Healing by fist intention

A clean wound with a minimum of space between the margins.

healing by first intention

( 参照武忠弼 病理学， 1998 修改 )

(2) Healing by second intention

Healing by second intention differs from healing by first intention in:

① Greater tissue loss ② More inflammatory exudates and

necrotic material to remove ③ More granulation tissue therefore

a bigger scar

healing by second intention ( 参照武忠弼 病理学， 1998 修改 )

④ Wound contraction necessary

⑤ Slower process

⑥ Increased liability to infection

(3) Healing under scab

4. Factors influencing wound healing

(1) Local factors adversely affecting (1) Local factors adversely affecting healinghealing

① Type of wounding agent; blunt, crushing, tearing etc.

② Infection

③ Foreign bodies in wound

④ Poor blood supply

⑤ Excessive movement

⑥ Poor apposition of margins, e. g. large haematoma formation

⑦ Poor wound contraction due to tissue tethering

⑧ Infiltration by tumor.

⑨ Previous irradiation.

(2) General factors adversely affecting healing

① Age

② Poor nutrition Deficiency of protein Lack of Vitamin C results in

abnormal granulation tissue and deficient collagen production

Zinc deficiency

③ Excessive glucocorticosteroid production or administration

④ Fall in temperature

⑤ Jaundice

(3) Factors accelerating wound healing

① Ultraviolet light.

② Administration of anabolic steroids, deoxycorticosterone acetate, cell growth factors.

③ Rise in temperature.