This document discusses tissue repair and wound healing. It begins by defining key terms like repair, regeneration, and healing. It then describes the phases of wound healing as inflammation, granulation tissue formation, and remodeling. The two main types of wound healing are primary intention for clean surgical wounds and secondary intention for wounds with more tissue loss. The process of each is described, involving inflammation, new blood vessel formation, collagen deposition, and epithelialization. Factors that influence healing like nutrition, infection, and wound size are also outlined. Complications can include dehiscence, contractures, and excessive scar formation.

1. TISSUE REPAIR
(WOUND HEALING)
DR. RAM THAPA

2. Course Content
Types, etiopathogenesis
Factors affecting Healings – Promoting &
Delaying
Mechanism of healing – Primary and secondary
intention

3. Definitions
Repair, also called healing, refers to the
restoration of tissue architecture and
function after an injury.
Repair is used for parenchymal and
connective tissues
Healing for surface epithelia,

4. Definitions:
Regeneration: refers to growth of cells and tissues to
replace lost structures
Healingis usually a tissue response
◦to a wound (commonly in the skin),
◦to inflammatory processes in internal organs, or
◦to cell necrosis in organs incapable of
regeneration.

6. Healing
Regeneration scar formation

9. When healing can not be accomplished by
regeneration, the main healing process is
repair by deposition of collagen and other
ECM components, causing the formation of
a scar.

10. 1. Labile Cells: epithelial cells,haematopoietic cells
of bone marrow
2.Stable cells:-Parenchymal cells of organs like liver,
pancreas, kidneys, adrenal and thyroid;
mesenchymal cells like smooth muscle cells,
fibroblasts, vascular endothelium
3.Permanent cells:- neurons of nervous system,
skeletal muscle and cardiac muscle cells

11. wound healing
Inflammation
Angiogenesis
Migration and proliferation of fibroblasts
Scar formation
Connective tissue remodelling

12. Wound healing
complex but orderly phenomenon involving a number of
processes:
1) Induction of an inflammatory process in response to the initial
injury
2) Proliferation and migration of parenchymal and connective
tissue cells
3) Formation of new blood vessels (angiogenesis) and
granulation tissue
4) Synthesis of ECM proteins and collagen deposition
5) Tissue remodelling
6) Wound contraction
7) Acquisition of wound strength

13. Cutaneous wound healing is generally divided
into three phases:
(1) inflammation (early and late);
(2) granulation tissue formation and re-epithelialization
(3) wound contraction, ECM deposition, and remodelling

14. Granulation Tissue Formation
Granular and pink appearance of the tissue with proliferation of
new small blood vessels, fibroblasts and young collagen.

15. Phases of cutaneous wound healing

16. PROCESS OF WOUND HEALING
1. Primary intention
2. Secondary intention

17. WOUND HEALING BY PRIMARY INTENTION
The healing of a clean, uninfected surgical
incision approximated by surgical sutures
Such healing is referred to as primary union
or healing by first intention

18. WOUND HEALING BY PRIMARY
INTENTION
Defined as healing of a wound which has the
following characteristics:
i) clean and uninfected;
ii) surgically incised;
iii) without much loss of cells and tissue; and
iv) edges of wound are approximated by surgical
sutures.

19. Healing process follows a series of
sequential steps:
Within 24 hours:
◦neutrophils appear at the margins of the
incision, moving toward the fibrin clot.

20. In 24 to 48 hours:
◦epithelial cells move from the wound edges
(with little cell proliferation) along the cut
margins of the dermis
◦Deposition of basement membrane components
as they move

21. By day 3:
◦neutrophils replaced by macrophages
◦Granulation tissue progressively invades the
incision space.
◦Collagen fibers are now present in the margins of
the incision, but at first these are vertically oriented
and do not bridge the incision.
◦Epithelial cell proliferation thickens the epidermal
layer

22. By day 5:
◦the incisional space is filled with granulation tissue.
◦Neovascularization is maximal.
◦Collagen fibrils  more abundant and begin to
bridge the incision.
◦differentiation of surface cells yields a mature
epidermal architecture with surface keratinization.

23. During the second week:
collagen +++
proliferation of fibroblasts ++
leukocytic infiltrate, edema, and increased
vascularity largely disappear
the long process of blanching begins,
accomplished by the increased accumulation of
collagen within the incisional scar, accompanied
by regression of vascular channels.

24. By the end of the first month:
◦Scar is made up of a cellular connective tissue
devoid of inflammatory infiltrate, covered now
by intact epidermis.
◦The dermal appendages  permanently lost.
◦Tensile strength of the wound increases

26. WOUND HEALING BY SECONDARY INTENTION
Occurs when there is
◦ more extensive loss of cells and tissue
◦ large defects in surface wounds
The reparative process is more complicated
Abundant granulation tissue grows in from the margin to
complete the repair.
referred to as secondary union or healing by second intention

27. HEALING BY SECOND INTENTION
Defined as healing of a wound having the following
characteristics:
i) open with a large tissue defect, at times infected;
ii) having extensive loss of cells and tissues;
iii) the wound is not approximated by surgical
sutures but is left open.

28. Differs from healing by primary intention by
the following points:
1. Large tissue defects  a larger fibrin clot that fills the
defect more necrotic debris and exudates that must be
removed. Inflammatory reaction is more intense.
2. Much larger amounts of granulation tissue are formed.
3. wound contraction
4. scar formation and thinning of the epidermis.

31. Development of fibrosis in chronic inflammation

32. HEALING OF SKIN ULCER
(A)Inflammation
(B)Proliferation of epithelial
cells; formation of
granulation tissue by vessel
growth proliferating
fibroblasts.
(C) Remodeling to produce the
fibrous scar.
Steps in repair by scar formation: wound healing in
the skin.

33. WOUND STRENGTH
After removal of sutures:
◦At the end of first wk  wound strength
is ~ 10% that of unwounded skin
◦After 3rd month  ~70% to 80% of normal
skin

34. FACTORS THAT INFLUENCE WOUND HEALING:
SYSTEMIC:
1. Nutrition Protein deficiency vitamin C
deficiency  inhibit collagen synthesis  retard
healing
2.Metabolic status  eg. Diabetes mellitus  retard
healing .
3.Circulatory status  eg. Inadequate blood supply 
arteriosclerosis or venous abnormalities (e.g.,
varicose veins)  retard venous drainage, also
impairs healing
4. Hormones  eg. glucocorticoids  inhibit collagen
synthesis  impairs healing

35. LOCAL:
1. Infection  persistent tissue injury and
inflammation.
2. Mechanical factors  early motion of wounds 
compressing blood vessels and separating the
edges of the wound.
3. Foreign bodies  unnecessary sutures or
fragments of steel, glass, or even bone
4. Size, location & type of injury
FACTORS THAT INFLUENCE WOUND
HEALING

36. COMPLICATIONS OF WOUND
HEALING
(1)Wound dehiscence and ulceration
◦ Inadequate formation of granulation
tissue or assembly of a scar
◦ inadequate vascularization
◦ diabetic peripheral neuropathy

37. (2) Formation of contractures:
•An exaggeration of
contraction gives rise to
contracture and results in
deformities of the wound and
the surrounding tissues.
•common sites: palms, the soles, and
the anterior aspect of the thorax

38. (3) excessive formation of the repair
components
◦ hypertrophic scar
◦ keloid
◦ exuberant granulation
◦ desmoids, or aggressive fibromatoses

39. Repair, regeneration, and fibrosis after injury and inflammation