The document discusses the processes of wound healing through regeneration and repair. Regeneration involves the proliferation of parenchymal cells to restore original tissues, while repair involves proliferation of connective tissue elements and fibrosis. Repair was described as occurring through granulation tissue formation and wound contraction. The phases of wound healing were explained as inflammation, clearance and ingrowth of granulation tissue. Primary and secondary wound healing were also summarized.

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2.  The body response to injury in an attempt to
restore normal structure and function.
 Involves 2 distinct processes:
◦ Regeneration: healing takes place by proliferation
of parenchymal cells and usually results in complete
restoration of the original tissues.
◦ Repair: healing takes place by proliferation of
connective tissue elements resulting in fibrosis and
scarring.
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3.  Repair is the replacement
of injured tissue by
fibrous tissue.
 Two processes are
involved in repair:
◦ Granulation tissue
formation;
◦ Contraction of wounds.
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4.  Th3 phases are observed in the formation of
granulation tissue
 PHASE OF INFLAMMATION
 PHASE OF CLEARANCE
◦ Combination of proteolytic enzymes liberated from
neutrophils, autolytic enzymes from dead tissues
cells
◦ phagocytic activity of macrophages clear off the
necrotic tissue, debris and red blood cells.
 PHASE OF INGROWTH OF GRANULATION
TISSUE
◦ 2 main processes: angiogenesis or
neovascularisation, and fibrogenesis
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5.  Wound starts contracting after 2-3 days and
the process is completed by the 14th day.
 Reduced by approximately 80% of its original
size
 This process aids in rapid healing – lesser
surface area of the injured tissue has to be
replaced
 It takes place in following step : Dehydration
and formation of myofibroblast (intermediate
between fibroblast and muscle cells.
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7.  Healing of skin wounds -
classical example of
combination of
regeneration and repair
 It can be accomplished in
one of the following
two ways:
◦ Healing by First intention
(primary union)
◦ Healing by Second intention
(secondary union)
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8.  Healing of a wound which has the following
characteristics:
◦ clean and uninfected;
◦ surgically incised;
◦ without much loss of cells and tissue; and
◦ edges of wound are approximated by surgical sutures
• The incision causes only focal disruption of
epithelial basement membrane continuity and
death of a relatively few epithelial and
connective tissue cells.
• As a result, epithelial regeneration
predominates over fibrosis.
• A small scar is formed, but there is minimal
wound contraction
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9.  Within 24 hours,
◦ neutrophils are seen at the incision margin, migrating
toward the fibrin clot.
◦ Basal cells at the cut edge of the epidermis begin to
show increased mitotic activity.
 Within 24 to 48 hours
◦ epithelial cells from both edges have begun to migrate
and proliferate along the dermis, depositing basement
membrane components as they progress.
◦ The cells meet in the midline beneath the surface scab,
yielding a thin but continuous epithelial layer
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10.  Neutrophils have been largely replaced by
macrophages,
 Granulation tissue progressively invades the
incision space.
 Collagen fibers are now evident at the
incision margins, but these are vertically
oriented and do not bridge the incision.
 Epithelial cell proliferation continues, yielding
a thickened epidermal covering layer.
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11.  neovascularization reaches its peak as
granulation tissue fills the incisional space.
 Collagen fibrils become more abundant and
begin to bridge the incision.
 The epidermis recovers its normal thickness
as differentiation of surface cells yields a
mature epidermal architecture with surface
keratinization.
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12.  There is continued collagen accumulation and
fibroblast proliferation.
 The leukocyte infiltrate, edema, and
increased vascularity are substantially
diminished.
 The long process of "blanching" begins,
accomplished by increasing collagen
deposition within the incisional scar and the
regression of vascular channels.
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A, The incised wound as well as suture track on either side are filled with
blood clot and there is inflammatory response from the margins.
B, Spurs of epidermal cells migrate along the incised margin on either side as
well as around the suture track. Formation of granulation tissue also begins
from below.
C, Removal of suture at around 7th day results in scar tissue at the sites of
incision

14.  Healing of a wound having the following characteristics:
◦ open with a large tissue defect, at times infected;
◦ having extensive loss of cells and tissues;
◦ the wound is not approximated by surgical sutures but is left
open.
• The basic events in secondary union are similar
to
primary union
• Differ in having a larger tissue defect which has
to be bridged.
• Hence healing takes place from the base
upwards as well as from the margins inwards
• Results in a large and sometimes ugly scar
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16.  Initial haemorrhage.
◦ As a result of injury, the wound space is filled with blood and
fibrin clot which dries.
 Inflammatory phase
◦ initial acute inflammatory response
◦ followed by appearance of macrophages which clear off the debris
as in primary union.
 Epithelial changes.
◦ As in primary healing, the epidermal cells from both the margins
of wound proliferate and migrate
◦ into the wound in the form of epithelial spurs till they meet in the
middle and re-epithelialise the gap completely.
◦ However, the proliferating epithelial cells do not cover the
surface fully until granulation tissue from base has started
filling the wound space
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17. • Granulation tissue
 Main bulk of secondary healing is by granulations.
 Granulation tissue is formed by proliferation of
fibroblasts and neovascularisation from the adjoining
viable elements.
 Its deep red, granular and very fragile.
 With time, the scar on maturation becomes pale and
white due to increase in collagen and decrease in
vascularity.
 Specialised structures of the skin like hair follicles and
sweat glands are not replaced unless their viable
residues remain which may regenerate.
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18. • Wound contraction.
 Its an important feature of secondary healing, not seen in
primary healing.
 Due to the action of myofibroblasts present in granulation
tissue, the wound contracts to one-third to one-fourth of
its original size.
 Wound contraction occurs at a time when active
granulation tissue is being formed.
• Presence of infection
 Bacterial infection may delays the process of healing due
to release of bacterial toxins
 These provoke necrosis, suppuration and thrombosis.
 Debridement: Surgical removal of dead and necrosed
tissue, helps in preventing the bacterial infection of open
wounds.
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A, The open wound is filled with blood clot and there is inflammatory
response at the junction of viable tissue.
B, Epithelial spurs from the margins of wound meet in the middle to cover
the gap and separate the underlying viable tissue from necrotic tissue at the
surface forming scab.
C, After contraction of the wound, a scar smaller than the original wound is
left.

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22.  Infection
 Implantation : epidermal cyst
 Pigmentation: rust-like colour due to staining with
haemosiderin.
 Deficient scar formation: inadequate formation of
granulation tissue
 Incisional hernia
 Hypertrophied scars and keloid formation: Excessive
formation of collagen in healing
 Excessive contraction: Dupuytren’s (palmar) contracture,
plantar contracture and Peyronie’s disease (contraction of
the cavernous tissues of penis).
 Neoplasia. Rare, e.g. squamous cell carcinoma in Marjolin’s
ulcer i.e. a scar following burns on the skin
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KELOID EPIDERMAL CYST

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Pigmentation of Wound Dupuytren’s (palmar) contractur

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27.  Fracture results in well defined tissue response to
remove the debris and to re-establish vascular
supply and to produce a new skeletal matrix.
 The timing and histology of process of healing is
dependent on location of fracture and local and
systemic factors.
 Depending on this factors healing take place in
either of two ways, i.e.:
◦ Primary Bone healing
◦ Secondary bone healing
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28.  It take place when in following condition
◦ Excellent anatomic reduction
◦ Minimal or no mobility
◦ Good vascular supply at fracture site
• It occurs in two different ways i.e.:
 Gap Healing
 Contact Healing
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29.  Even with excellent rigid
fixation, a perfect
anatomic reduction rarely
exist due to deforming
forces like muscle pull
and function
 In such cases blood
vessels from periosteum,
endosteum and haversian
canal invade the gap,
bridging mesenchymal
osteoblastic precussors.
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30.  Bone is directly deposited on the fracture
fragmenst without resorption and cartilage
formation.
 Gap = < 0.3 mm – lamellar bone forms
directly.
 Gap = 0.3 – 1mm woven bone forms first
followed by lamellar bone
 Healing takes place over 6 weeks.
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31.  When there is adequate contact, essentially a
zero gap, then healing take place through
contact heatling.
◦ There is Osteoclastic activity at the fracture ends which
results in bone resorption and finally remodelling by
Bone metabolising unit (BMU), Bone repair unit (BRU),
and bone remodelling unit (BRU).
• There is formation of osteon which forms
the bone again between gap created in
remodelled bone.
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32.  It take place in fracture without surgical
intervention and after semi-rigid fixation.
 It takes place in four stages:
◦ Intermediate reaction
◦ Procallus formation
◦ Osseous callus formation
◦ Remodelling
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A, Haematoma formation and local inflammatory response at the fracture site.
B, Ingrowth of granulation tissue with formation of soft tissue callus.
C, Formation of procallus composed of woven bone and cartilage with its
characteristic fusiform appearance and having 3 arbitrary components —
external, intermediate and internal callus.
D, Formation of osseous callus composed of lamellar bone following clearance
of woven bone and cartilage.
E, Remodelled bone ends; the external callus cleared away. Intermediate callus
converted into lamellar bone and internal callus developing bone marrow cavity

34.  Robbinson's basic pathology 8 ed
 Harsh Mohan - Textbook of Pathology 6th Ed.
 Color atlas of pathology
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