Cutaneous wound healing occurs through first or second intention. Primary union (first intention) involves clean surgical incisions approximated by sutures, resulting in relatively thin scar formation. Secondary union (second intention) involves larger defects without sutures, resulting in formation of granulation tissue and more substantial scarring due to wound contraction. The stages of wound healing include formation of a blood clot, granulation tissue, re-epithelialization, collagen deposition, and scar formation.

1. CUTANEOUS WOUND
HEALING
BY
FIRST AND SECOND
INTENTION
By:
Dr. Kinz

2. CUTANEOUS WOUND HEALING

3. STAGES OF NORMAL CUTANEOUS
WOUND HEALING

4. CLASSIFICATION OF WOUND
HEALING
A. Primary Union (First Intention)
• Clean uninfected surgical incision approximated by
sutures.
• Death of limited number of epithelial and connective
tissue.
• Basement membrane damage is minimal.
• Relatively thin scar formation.

5. B. Secondary Union (Second Intention)
• Larger defects, the edges are not attached properly,
formation of granular tissue.
• Extensive loss of cells and tissues with intense
inflammatory reaction and collagen formation.
• Fibrin clot is larger, there is more exudate and necrotic
debris.
• Granular tissue substantial scar formation which
contracts.
• Involves wound contraction.

6. FORMATION OF BLOOD CLOT
• Activation of coagulation pathways leading to clot
formation which prevents bleeding
• Release of Vascular Endothelial Growth Factor(VEGF)
with increased permeablity and edema
• Dehydration at the external surface of clot makes a scab
that covers the wound.
• Larger fibrin clot is seen in healing by second intention
with more exudate and necrotic debris in the wound.

7. • Within 24 hours, neutrophils appear at the margins of
the incision.

8. FORMATION OF
GRANULATION TISSUE
• Hallmark of repair.
• Occurs in the first 24 to 72 hours due to fibroblast and
vascular endothelial cell proliferation.
• Soft, pink and granular appearance on the surface of
wounds.
• The newly formed blood vessels are leaky leading to
passage of plasma proteins and fluid into extravascular
space – edematous in appearance.
• By 5 to 7 days the granulation tissue fills up the wound area
(more pronounced effect in healing by second intension).

10. CELL PROLIFERATION AND
COLLAGEN DEPOSITION
• Neutrophils are replaced by macrophages by 48 to 96 hours
which play role in clearing extracellular debris, fibrin and
other foreign material, promoting angiogenesis and
extracellular matrix deposition
• Fibroblast migration by chemokines and their subsequent
proliferation
• Deposition of collagen at the margins of the incision –
vertically oriented in primary intention and horizontally
oriented in secondary intention

11. • In 24 to 48 hours proliferation and migration of epithelial
cells adjacent to wound, migration to the margins of dermis,
depositing basement membrane components.
• Epithelial cell proliferation thickens.
• collagen fibrils (type I collagen) become more abundant and
bridges the incision.

12. EPITHELIZATION

13. SCAR FORMATION
• By second week, there is increased accumulation of
collagen with regression of vasculature.
• The granulation tissue is converted into pale, avascular scar
composed of spindle shaped fibroblasts, dense collagen,
also there is elastic tissue, and other extracellular matrix
components.

14. WOUND CONTRACTION
• Primarily occurs in healing by secondary intention.
• Formation of myofibroblasts from the tissue fibroblasts.
• These cells contract in the wound and produce large amount
of extracellular martrix components.

16. CONNECTIVE TISSUE
REMODELING
• The balance between extracellular matrix synthesis and
degradation results in remodeling of connective tissue
framework
• Matrix metalloproteinases e.g. interstitial collagenases,
gelatinases degrade the ECM, and are inhibited by Tissue
Inhibitors of metalloproteinases .

17. RECOVERY OF TENSILE
STRENGTH
• Tensile strength in healing wound is provided my fibrillar
collagens (type I collagen) with cross linking and increased
fibre size.
• Sutures are removed typically at first week, the wound
strength is 10% of normal.
• By 3rd month the strength plateaus upto 70 to 80% of
normal.