Any violation of live tissue integrity may be regarded
as a wound
Skin is the largest organ of the human body.
Acute wound- orderly and timely reparative
process - laceration, puncture, abrasion, avulsion,
Chronic wound – wound not healed in 4 weeks.
Venous and arterial ulcers, diabetic ulcers, pressure
Three techniques of wound
Primary intention- all tissue including skin are closed
with suture material.
Secondary intention – in which wound is left open
and close naturally.
Tertiary intention – in which wound is left open for
number of days and then closed if it found to be
DEFINITION – wound healing
Response of an organism to a physical disruption of a
tissue/organ with an aim to repair or reconstitute the
defect and to re-establish homeostasis.
Can be achieved by 2 processes: scar formation &
Dynamic balance between these 2 is different in
During healing, a complex cascade of cellular events
occur to achieve resurfacing, reconstitution and
restoration of tensile strength of injured tissue.
3 classic but overlapping phases occur: inflammation,
proliferation & maturation.
Early Wound Healing Events (Days 1-4)
A. Inflammatory or reactive phase
- immediate response to injury
- goals: hemostasis, debridement , sealing of the
1. Increase vascular permeability
3. Secretion of cytokines
4. Growth factor
Blood vessels are disrupted, resulting in bleeding.
Hemostasis is achieved by formation of platelet plug
& activation of extrinsic(initiation) & intrinsic
Formation of a provisional fibrin matrix.
Recruitment of inflammatory cells into the wound by
Fibrin and fibronectin form a lattice that provides
scaffold for migration of inflammatory,
endothelial, and mesenchymal cells.
Neutrophilic infiltrate appears: removes dead
tissue & prevent infection.
Monocytes/macrophages follow neutrophils:
orchestrated production of growth factors &
- Migration of PMN stops when wound
contamination has been controlled
- Don’t survive more than 24 hours
- Increase contamination stimulates PMN
resulting to delayed wound healing and
destruction of tissues.
- Not essential for wound healing
- Orchestrate release of cytokines/ Process
of wound healing/ release of growth
- 24 – 48 hours
- Source of TNF /interleukin 1, 6, 8
Granulation tissue formation (composed of
fibroblasts, macrophages and emdothelial cells).
Re-epithelialization (begins immediately after injury)
Decrease collagen synthesis at 4 weeks after
- Scaffold for cellular migration
- Composed of fibrin, fibrinogen,
Fibronectin and type 3 collagen = early
Type 1 collagen – wound strength later
Mesenchymal cell proliferation
Fibroblasts are the major mesenchymal cells involved
in wound healing, although smooth muscle cells are
Macrophage products are chemotactic for fibroblasts.
PDGF, EGF, TGF, IL-1, lymphocytes are as well.
Replacement of provisional fibrin matrix with type III
Angiogenesis reconstructs vasculature in areas
damaged by wounding, stimulated by high lactate
levels, acidic pH, decreased O2 tension in tissues.
Recruitment & assembly of bone marrow derived
progenitor cells by cytokines is the central theme.
FGF-1 is most potent angiogenic stimulant
identified. Heparin important as cofactor, TGFalpha, beta, prostaglandins also stimulate.
Basal cell layer thickening, elongation,
detachment & migration via interaction with ECM
proteins via integrin mediators.
Generation of a provisional BM which includes
fibronectin, collagens type 1 and 5.
Epithelial cells proliferation contributes new cells
to the monolayer. Contact inhibition when edges
By three keratinocyte functions – migration ,
proliferation and differentiation.
Goal: scar contraction with collagen cross-
linking, shrinking and loss of edema
Programmed regression of blood vessels &
Wound contraction – centripetal movement
of full thickness of skin
Decreases amount of disorganized scar
Wound contracture, physical restriction,
limitation of function- result of wound
Appearance of stimulated fibroblast known
Fetal Wound Healing
Younger the fetus less noticeable is the scar
Fetal fibroblasts even in adult transplantation heals with the
absence of inflammation
Theory: that wound fibroblasts do not become myofibroblasts
until late in gestation.
IL6 is high in adult stimulated fibroblasts compared to fetal
stimulated ones with coincides with increased inflammation in
Thrombospondin 1 decreases with increase in gestation. It
destabilizes matrix contracts in the EC space, facilitates
mitogenesis and chemotaxis. Promotes cell associated protease
and self supports matrix turnover. Thus inflammation would
decrease and there would be less scarring
19 types identified. Type 1(80-90%) most common,
found in all tissue. The primary collagen in a healed
Type 3(10-20%) seen in early phases of wound
healing. Type V smooth muscle, Types 2,11 cartilage,
Type 4 in BM.
Begins approximately 4-5 days after wounding by
action of myofibroblasts.
Represents centripetal movement of the wound edge
towards the center of the wound.
Maximal contraction occurs for 12-15 days, although it
will continue longer if wound remains open.
The wound edges move toward each other at an
average rate of 0.6 to .75 mm/day.
Wound contraction depends on laxity of tissues, so a
buttock wound will contract faster than a wound on
the scalp or pretibial area.
Wound shape also a factor, square is faster than
Contraction of a wound across a joint can cause
Can be limited by skin grafts, full better than split
The earlier the graft the less contraction.
Splints temporarily slow contraction.
After 21 days, net accumulation of collagen becomes
stable. Bursting strength is only 15% of normal at this
point. Remodeling dramatically increases this.
3-6 weeks after wounding greatest rate of increase, so
at 6 weeks we are at 80% to 90% of eventual strength
and at 6months 90% of skin breaking strength.
The number of intra and intermolecular cross-
links between collagen fibers increases
A major contributor to the increase in wound
Quantity of Type 3 collagen decreases replaced by
Type 1 collagen
Remodeling continues for 12 mos, so scar revision
should not be done prematurely.
Diabetes- impaired neutrophil chemotaxis,
Steroids and immunosuppression suppresses
macrophage migration, fibroblast proliferation,
collagen accumulation, and angiogenesis.
Reversed by Vitamin A 25,000 IU per day.
Excessive Scar Formation
Excessive healing results in a raised, thickened
scar, with both functional and cosmetic
If it stays within margins of wound it is
hypertrophic. Keloids extend beyond the confines
of the original injury.
Dark skinned, ages of 2-40. Wound in the
presternal or deltoid area, wounds that cross
Keloids and Hypertrophic Scars
Keloids more familial
Hypertrophic scars develop soon after injury, keloids
up to a year later.
Hypertrophic scars may subside in time, keloids
Hypertrophic scars more likely to cause contracture
over joint surface.
Keloids and Hypertrophic Scars
Both from an overall increase in the quantity of
Recent evidence suggests that the fibroblasts within
keloids are different from those within normal dermis
in terms of their responsiveness.
No modality of treatment is predictably effective for