This topic is mainly for MBBS Studnts. It is under the General Principles of Surgery. Students shoud know the phases of wound healing so as to treat them appropriately and select the correct method of dressing material....

1. Prof. U. Murali.
Wound Healing

2. Learning Objectives
•Introduction
•Phases of wound healing
•Types of wound healing
•Factors of wound healing
•Complications

3. • Wound healing is a complex and
dynamic biological process.
• It is related to tissue reconstitution
which is the process by which the body
replenishes cells that are being lost.
• All wounds heal following a specific
sequence of phases which may
overlap.
• The process of wound healing depends
on the type of tissue which has been
damaged and the nature of tissue
disruption.
Introduction

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• Classically, wound healing has been
arbitrarily described in 3 overlapping
but distinct stages / phases and include:
• Inflammatory phase
[ Lag / Substrate / Exudative phase ]
• Proliferative phase
[ Collagen / Fibroblastic phase ]
• Remodeling phase
[ Maturation phase ]
Phases of Wound Healing

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• It begins immediately after wounding & and
lasts 2–3 days.
• Hemostasis, is often described as the
immediate phase occurring before
inflammation.
• Hemostasis is achieved by vasoconstriction
with formation of platelet plug [PT adhere,
activate and aggregate] & activation of
clotting pathway, resulting in formation of
fibrin matrix.
• The fibrin clot helps to stabilize the platelet
plug and form a scaffold for migration of
inflammatory cells [PMLs] into the wound.
I. Phase – H & I

6. • In the early inflammatory phase (days 1–2),
platelet activation causes an influx of
inflammatory cells led by PMLs, particularly
neutrophils.
• Neutrophils – the first infiltrating cells to
enter the wound site.
• They are important for minimizing bacterial
contamination of the wound, by
phagocytosis.
• Platelets and the local injured tissue release
vasoactive amines such as histamine &
serotonin, which increase vascular
permeability, thereby aiding infiltration of
further inflammatory cells.
I. Inflammatory Phase - Early

7. • During the late inflammatory phase (days 2–3)
monocytes appear in the wound and
differentiate into macrophages.
• Macrophages play a vital role in wound healing.
• They function as phagocytic cells and release
proteolytic enzymes to help debride the
wound.
• They are also the primary producer of cytokines
and growth factors promoting fibroblast
proliferation & angiogenesis.
• Historically, this phase has been described by
rubor (redness), tumor (swelling), calor (heat)
and dolor (pain) – RTCD.
I. Inflammatory Phase - Late

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• The proliferative phase starts around
day 3 and lasts for 2–4 weeks.
• It is during this phase that the wound
continuity is re-established.
• It consist mainly of fibroblast activity
with the production of collagen &
ground substance (glycosaminoglycans
and proteoglycans).
• Also, the growth of new blood vessels
as capillary loops (angio-neogenesis) &
the re-epithelialization of the wound
surface.
II. Proliferative Phase

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• The wound tissue formed in the early
part of this phase is called granulation
tissue (contains fibroblasts,
macrophages & endothelial cells).
• It has a pink and granular appearance.
• Some fibroblasts differentiate into
myofibroblasts, which are contractile
cells.
• These play an important role in
contraction to bring the edges of the
wound together.
II. Proliferative Phase

10. • In the latter part of this phase, there is an
increase in the tensile strength of the
wound due to increased collagen, which is
at first deposited in a random fashion and
consists of type III collagen.
• Initial angiogenesis occurs following
release of factors from keratinocytes &
macrophages.
• Later re-epithelialization of the wound
surface occurs by migration of basal layer
of the retained epidermis which
proliferates, differentiates and stratifies to
form wound closure.
II. Proliferative Phase

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• The remodeling phase begins 2–3
weeks after injury and lasts for a
year (or) more. This phase is
characterized by maturation of
collagen.
• Type III collagen, which is
prevalent during proliferation, is
replaced by stronger type I
collagen until the normal skin
ratio of 4:1 type I to type III
collagen is re-established.
III. Remodeling Phase

12. • The collagen becomes more
cross-linked and uniformly
aligned.
• This maturation of collagen leads
to increased tensile strength in
the wound/scar, which is maximal
12 weeks post injury and
represents approximately 80% of
the uninjured skin strength.
• The final matured scar is acellular
and avascular.
III. Remodeling Phase

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• Wound healing is accomplished in one of
the following 3 ways –
• Healing by primary intention
[wounds with opposed edges]
• Healing by secondary intention
[wounds with separated edges]
• Healing by tertiary intention
[tertiary wound healing]
Types of Wound Healing

17. • It occurs in a clean incised wound (or)
surgical wound with good apposition of
the edges.
• The incision causes only focal disruption
of epithelial BM continuity & death of a
relatively few epithelial connective
tissue cells.
• As a result, there is more epithelial
regeneration than fibrosis.
• Wound heals rapidly with complete
closure and leaving best scar. Scar will
be linear, smooth, and supple.
Primary Intention

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• This occurs in open wounds,
particularly when there has been
significant loss of tissue, or
wounds with irregular margins.
• Regeneration of parenchymal cells
cannot completely reconstitute
the original architecture.
• It heals slowly with fibrosis. It leads
into a wide scar, often
hypertrophied and contracted. It
may lead into disability.
Secondary Intention

19. • Delayed primary healing occurs when
the wound edges are not opposed
immediately, which may be necessary
in contaminated or untidy wounds.
• After debridement of non-viable
tissue and when the wound is clean,
the wound edges may be surgically
approximated. This is also called
healing by tertiary intention.
• Primary contaminated or mixed
tissue wounds heal by tertiary
intention.
Tertiary Intention

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24. • Various factors can adversely affect
wound healing and include –
•Local Factors
•Systemic / General Factors
Factors - Wound Healing

55. Complications – W H
• Excessive Scar Formation: Hypertrophic scar,
Keloid.
• Deficient Scar Formation: Result in wound
dehiscence [or] rupture of the wound due to
inadequate formation of granulation tissue.
• Exuberant Granulation (Proud Flesh):
Excessive GT that protrudes above the skin
level.
• Deficient contraction – Skin grafts
Excessive contraction – In Burns
• Others: Pigmentary changes, Incisional
hernia, Dystrophic calcification, Neoplastic
changes.

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• Phases of wound healing.
• The changes in each phases - pathophysiology.
• Types of wound healing.
• Factors affecting wound healing – Local & Systemic factors.
• Complications of wound healing.
To Summarize

57. References

58. • Explain the first phase of wound healing.
• List 4 differences between 1 & 2 union of wound healing.
• Enumerate 5 local factors affecting wound healing.
• Mention the complications of wound healing.
• Write about tertiary intention.
• Illustrate with flow-chart the phases of wound healing.
• Describe the nutritional deficiencies affecting wound healing.
• Write the stages of wound healing.
Question Time

59. Factors impairing wound healing include all the
following, except –
◼ a) Excessive tension.
◼ b) Lack of hemostasis.
◼ c) Inversion of wound edges.
◼ d) Drains.
◼

60. The tensile strength of the wound starts and
increases after –
◼ a) Immediate suture of the wound.
◼ b) 3 – 4 days.
◼ c) 7 – 10 days.
◼ d) 6 months.
◼

61. Which one of the following cells plays an
important role in bringing the edges of the
wound together? –
◼ a) Myofibroblasts.
◼ b) Macrophages.
◼ c) Polymorphonuclear leukocytes.
◼ d) Fibroblasts.
◼

62. Factors that may adversely affect the healing
of wounds include all the following, except –
◼ a) Exposure to radiation.
◼ b) Advanced neoplasia.
◼ c) Exposure to UV light.
◼ d) Obstructive jaundice.
◼

63. When is the maximum collagen content of
wound tissue? –
◼ a) 2 – 5 days.
◼ b) 6 – 10 days.
◼ c) 11 – 16 days.
◼ d) 17 – 21 days.
◼

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