1. Lecture # 32 TISSUE REPAIR: REGNERATION, HEALING & FIBROSIS - 4 Dr
Lecture # 32 TISSUE REPAIR: REGNERATION, HEALING & FIBROSIS - 4 Dr. Iram Sohail Assistant Professor Pathology College Of Medicine Majmaah University

2. OBJECTIVES
Explain the mechanism of cutaneous wound healing
Discuss healing by first intension
Discuss healing by second intention
Discuss wound strength
Explain the pathological aspects & overview of repair process

3. Cutaneous wound healing
(Healing of skin wound)
This process involves the epithelial regeneration & formation of connective scar.
This re-epithelialization occurs mostly by migration of cells from edges of wound.

4. The growth factors involved are

5. Cutaneous wound healing has 3 phases
Inflammation
Formation of granulation tissue
ECM deposition & remodeling

6. Healing of cutaneous wound occurs by
Healing by first intention Or
Healing by second intention

8. Healing by first intention
It is the healing of a clean, uninfected, surgical incision approximated by surgical sutures.
A small scar is formed with minimum wound contraction.

9. Sequence of events Within 24 hours 24 to 48 hours
Fibrin clot is formed
Neutrophils
24 to 48 hours
The epithelial cells from both edges begin to migrate and meet in midline & a thin continuous epithelial layer is formed.

10. Day 3 Neutrophils are replaced by macrophages
Starting of granulation tissue formation
Collagen fibers appear
Thick epithelial layer is formed

11. Day 5 Neovascularization & granulation tissue formation completed
More collagen fibers
Epidermis recovers its normal thickness
Surface keratinization

12. 2nd week First month Increased fibroblast & collagen deposition
Vascular channels regress
First month
A scar is formed, composed of connective tissue
No inflammatory cells
Covered by normal epidermis
Dermal appendages (sweat gland, hair follicles) are destroyed permanently

15. Healing by second intention
When tissue loss is more extensive, such as in large wounds, ulceration, abscess formation, the repair process is more complex and called healing by second intension.

16. Inflammatory reaction is more intense with more granulation tissue along with wound contraction.
Accumulation of ECM and large scar formation.
Larger clot formation, rich in fibrin
Much larger granulation tissue is formed
Great scar formation
Wound contraction (myofibroblasts)

20. Wound strength
A carefully sutured wound has 70% strength of normal (unwounded) skin.
Wound strength is caused by increased collagen synthesis.
The strength of wound progresses rapidly and reaches at 70—80% at 3 month, but does not improve beyond this.

21. Pathological aspects of wound healing
Following factors can alter the quality of wound healing
Infection
Delays wound healing

22. Protein deficiency Vitamin . C - deficiency Delays wound healing
Delays wound healing (because of decrease collagen synthesis)

23. Glucocorticoid (Steroid) administration
Delays wound healing (because steroids cause decrease fibrosis)
Local pressure or torsion
Poor wound healing
Poor perfusion of blood
Delays wound healing

24. Diabetes mellitus Foreign body Poor wound healing
(Such as glass, steel)
delays wound healing

25. Keloid
Accumulation of very big amount of collagen in wound can result in a prominent, raised, ugly looking scar, known as keloid.
More common in blacks
It is mostly heritable (transfer from parents to children)

27. Overview of repair process