WOUND HEALING AND REPAIR OF TISSUES.ppt

Primary wound healing

1. WOUND HEALING AND
REPAIR OF TISSUES
Dr. J. Karthikesh MD

2. REPAIR
Granulation tissue formation
It is granular and pink in color, hence the
name
There are 3 phases in its formation
1.Phase of Inflammation – mediated
immediately after trauma by PMN, mac’s
2.Phase of clearance – done by proteolytic
enzymes liberated by PMN, dead cells. Mac’s
phagocytose necrotic tissue and RBC
3.Phase of ingrowth – Has 2 important steps
a. Angiogenesis
b. Fibrogenesis

3. Angiogenesis
Means formation of new blood vessels -
Neovascularisation
This is done by proliferation of new blood vessels
from the margins of severed blood vessels.
Initially the proliferated endothelial cells are solid
buds.
Within a few hours they develop a lumen and start
carrying blood. But these vessels are leaky.
With time, the leaky vessels are converted to form
capillaries, arterioles and venules.
The whole process is influenced by VEGF, PDGF,
TGF-b, bFGF.

4. Fibrogenesis
The new fibroblasts originate from fibrocytes and by
mitotic division of fibroblasts
Collagen is laid down on the 6
th
day to provide
strength and elasticity to the repaired wound.
As more fibrous tissue formation occurs and as more
collagen is laid down, a scar is formed.

5. Types of Wound Healing
Healing by Primary Union
Healing by Secondary Union

6. Primary Union
Healing of a wound that is
Clean & uninfected
Surgically incised
Without much loss of tissue
Edges approximated by sutures
Results in a neat scar

7. Sequence of events
Initial hemorrhage – space between the cut skin is
filled with blood which clots and seals the wound
against infection.
Acute inflammatory response – Mediated by
PMN’s initially and later by Mac’s
Epithelial changes – Basal cells of the epidermis
from the cut edges proliferate and migrate towards
the cut area and form a layer. This separates the
underlying viable tissue from the overlying dead
tissue (scab). By the 5
th
day a new layer of epidermis
is formed.
Organisation – Mediated by fibroblasts which move
in on day 3. By 5
th
day, collagen is laid down giving
strength to the wound. By 4 weeks, scar tissue is
formed.

9. Healing by Secondary
Union
Occurs when a wound is
Open with a large defect
Infected
Extensive loss of tissue
Not approximated by sutures
Results in an ugly scar formation

10. Sequence of events
Initial hemorrhage
Inflammatory phase
Epithelial proliferation – from both the basal layers
and superficial layers of the cut margins. Yet, the
cells do not cover the wound completely and hence
granulation tissue is formed.
Wound contraction – seen in secondary healing only.
By the action of myofibroblasts, the wound contracts
to 1/3
rd
or 1/4
th
its size.

12. Complications
Infection – delays healing
Implantation – epidermal cyst formation
Pigmentation – due to hemosiderin
Deficient scar formation
Incisional hernia
Hypertrophied scars
Excessive contracture–Dupytrens palmar contracture
Neoplasia – Sq.Cell Carcinoma in Marjolins ulcer

13. FRACTURE HEALING
Healing of a fracture depends on
Traumatic # (previously normal bone)
Pathological # (already diseased bone)
Complete # or Incomplete #
Simple # (closed), Compound #
(communicating to the skin surface) or
Comminuted # ( splintering)

14. Fracture healing by
secondary union
This is the common process of #
healing
It is described under 3 headings
Procallus formation
Osseous callus formation
Remodelling

15. Procallus formation
Steps involved in the formation of the procallus are
1.Hematoma – forms due to bleeding from the severed blood
vessels. Loose fibrin meshwork is formed which then lays the
foundation for Granulation tissue formation.
2.Local inflammatory response – then cleared away by
macrophages and osteoclasts
3. Ingrowth of granulation tissue with neovascularisation and
proliferation of mesenchymal cells from periosteum and
endosteum. A soft tissue callus is thus formed which unites
the ends of the #ed bones. However, it is not strong.
4.Callus composed of woven bone and cartilage – The cells of
the inner layer of the periosteum have osteogenic potential.
They lay down collagen and osteoid matrix within the
granulation tissue. The osteoid undergoes calcification and is
called woven bone callus. This is spindle in shape and unites
the ends of the bone. This is called PROCALLUS. It is
arbitrarily divided into External, Intermediate, Internal procallus

17. Osseous callus
formation
The procallus acts as the scaffolding on
which osseous callus composed of lamellar
bone is formed.
Woven bone is cleared away by osteoclasts
Calcified cartilage disintegrates
Newly formed blood vessels and osteoblasts
invade, laying down osteoid which is calcified.
Haversian canals develop forming lamellar
bone.

19. Remodelling
This occurs simultaneously during the
formation of lamellar bone
It is done by osteoclasts (bone clearing cells)
which work along with osteoblasts (bone
forming cells)
The external callus is cleared away, the
intermediate callus becomes the cortex and
the internal callus becomes the bone marrow

21. Complications of # healing
Fibrous union
Non-union
Delayed union