2. Tissue
Repair/Healing
• Repair, sometimes called healing refers to the
restoration of tissue architecture and function
after an injury.
• Repair of damaged tissues occurs by two
types of reactions:
1. Regeneration.
2. Connective tissue deposition (scar
formation).
3. Tissue
Repair/Healing
• Regeneration: is complete restitution of lost
tissue components identical to those
removed or killed by proliferation of residual
(uninjured) cells and maturation of tissue
stem cells.
• Connective tissue deposition (scar formation):
If the injured tissues are incapable of
regeneration, or if the the tissue is severely
damaged, repair occurs by the deposition of
connective tissue.
4. Tissue
Repair/Healing
• Regeneration occurs for example, in the
rapidly dividing epithelia of the skin and
intestines, and in some parenchymal
organs, notably the liver.
• Scar formation takes place in fibrosis of
the lungs, liver, kidney and in Myocardial
Infarction.
8. Tissue
Regeneration
• Both regeneration and scar formation
contribute in varying degrees to the
ultimate repair.
• Both processes involve the proliferation of
various cells, and close interactions
between cells and the extracellular matrix
(ECM).
• The cell proliferation in regeneration and
9. Tissue proliferative
activity
1.Continually dividing cells (labile
tissues): These cells proliferate
through-out life.
Epithelium of the skin, GIT and cells of bone
marrow. 2.Quiescent cells (Stable tissue):
Have a low level of replication. Cells from
these tissue can undergo rapid division in
response to stimuli. parenchymal cells of
liver and kidneys.
3.Non-dividing (permanent cells):
Cells that can not undergo mitotic division in
10. Granulation
tissue
• Granulation tissue is the hallmark of
healing. Granulation tissue progressively
invades the site of injury.
• The term granulation tissue derives from
its pink, soft, granular appearance seen in
area of ongoing wound healing.
11. Granulation
tissue
• Granulation tissue is:
i. the proliferation of fibroblasts
ii. new thin-walled, delicate
capillaries (angiogenesis), in a
loose extracellular matrix.
iii. admixed inflammatory cells,
mainly macrophages.
13. Healing of skin
wound
• Healing of skin wound is a process that
involves both epithelial regeneration and
the formation of connective tissue scar.
• Based on the nature and size of the
wound, the healing of skin wounds
occurs by first or second intention.
14. Healing of skin
wound
Healing by first intension
• When the injury involves only the epithelial
layer and the principal mechanism of
repair is epithelial regeneration it is called
primary union or healing by first intention.
• It is the process of healing of a clean,
uninfected surgical incisions
approximated by sutures.
15. Healing by second
intension
• Healing by second intention is also
known as healing by secondary union.
• When cell or tissue loss is more extensive
like in large wounds, abscesses,
ulceration, and ischemic necrosis
(infarction) in parenchymal organs.
• The repair process in second intension
involves a combination of regeneration
and scar formation.
16. Difference
between
Primary intension
1. Inflammatory
reaction is less
marked.
2. No wound
contraction.
3. Margins are
apposed
together.
4. Minimal tissue
damage
5. Minimal bleeding
6. Heals quickly
Secondary intension
1. Intense
inflammation.
2. Much granulation
tissue formation.
3. Gap persists
between margins.
4. Marked damage
of tissues.
5. More bleeding.
6. Takes time to heal.
7. Large scar
18. Angiogenesis
New blood vessel development from existing vessel
Steps:
- Vasodilation
- Separation of pericytes and disintegration of BM
- Migration of endothelial cells
- Proliferation of endothelial cells behind leading tip
- Recruitment of periendothelial cells
- Suppression of endothelial proliferation and deposition of
BM
19.
20. Growth factors – VEGF, FGF, PDGF, TGF beta
Notch signalling – crosstalk with VEGF
Regulates sprouting and branching of
vessel
21. Factors influencing wound
healing
Systemic factors:
1.Nutritional status: Protein deficiency and
vitamin C deficiency inhibit collagen synthesis
and delay wound healing.
2.Metabolic status: DM is associated delay in
wound healing.
3.Circulatory status, poor perfusion: Inadequate
blood supply impair wound healing.
4.Hormones: Glucocorticoids have anti-
inflammatory effects and inhibits collagen
synthesis causing delay.
22. Factors influencing wound
healing
Local factors:
1.Infection (one of the most important cause of
delay in healing).
2.Mechanical factors (increased local
pressure, high mobility delays healing).
3.Foreign bodies (splinter, steel, glass delays
healing).
4.Size and shape of wound (clear cut surgical
wound heals quickly).
5.Location of the wound (wound in the face
heals quickly)
23. Complications of wound healing
Complications of wound healing are
grouped into three categories:
i. Deficient scar formation.
ii. Excessive scar formation.
iii.Exuberant granulation tissue
formation
iv.Formation of contractures.
24. Complications of wound healing
Deficient scar formation can lead to two
types of complications:
1.Dehiscence or rupture of a wound.
2. Ulceration.
Wound dehiscence is common after
abdominal surgery and is due to
increased abdominal pressure.
Wounds ulceration is due to inadequate
vascularization. Example lower extremity
wounds in with atherosclerosis.
25. Complications of wound healing
Excessive scar formation can give rise to:
(1) hypertrophic scar
(2)keloids.
• The accumulation of excessive
amounts of collagen give rise to a
hypertrophic scar.
• If the scar tissue grows beyond the
boundaries of original wound and does
not regress, it is called keloid.
27. Exuberant granulation
tissue
• Exuberant granulation is the formation of
excessive amounts of granulation tissue,
which protrudes above the level of the
surrounding skin and blocks re-
epithelialization (proud flesh).
• Excessive granulation must be removed by
cautery or surgical excision to allow re-
epithelialization.
28. Wound
Contracture
• An exaggeration of contraction of wound
gives rise to contracture and results in
deformities of the wound and the
surrounding tissues.
• Common areas affected palms, the soles
and the anterior aspect of the thorax.
• Contractures are commonly seen after
serious burns which compromise
30. Remodeling of Connective
Tissue
• The connective tissue in the scar
continues to be modified and remodeled.
• To increase the strength
- cross linking of collagen
- Change of collagen from type III to type I
