TISSUE REPAIR
&
WOUND HEALING
DR. SALEEM SHAIKH
 1. what is inflammation? Write the types and signs of
inflammation. Explain in detail about the events in
acute inflamm
 2. Define neoplasia? Enumerate the types of
neoplasia. Explain in detail the characteristic of
neoplasia.
INTRODUCTION
 Healing is the body response to injury in an attempt to
restore normal structure and function.
 Healing involves two 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.
 Both the processes may take place simultaneously.
REGENERATION & REPAIR
 Some cells of the body have a short life span whereas others may have a
longer life span. In order to maintain the proper function of the tissues
the cells are under constant control of growth factors, which regulate
their cell cycle.
 Some mature cells of the body do not divide at all, while some cells
complete a cell cycle in 16-24 hrs.
 Depending on their capacity to divide the cells can be grouped onto 3
categories:
 Labile cells
 Stable cells
 Permanent cells
REGENERATION & REPAIR
 Labile cells: these cells continue to multiply throughout life under
normal physiologic conditions. Eg – epithelial cells of epidermis,
respiratory tract and cervix, haematopoietic cells of bone marrow and
cells of lymph nodes and spleen
 Stable cells: these cells lose their ability to multiply after maturity but
retain the capacity to multiply in response to stimuli throughout adult
life. Eg – parenchymal cells of liver, pancreas and kidney, fibroblast,
smooth muscle cells.
 Permanent cells: these cells lose their ability to proliferate around the
time of birth. Eg – neurons, cardiac muscle cells.
 Labile and stable cells have more chance of healing by regeneration,
whereas permanent cells heal by repair.
WOUND HEALING
 Healing of skin and mucosal wounds provides a classical example of
combination of repair and regeneration.
 Wound healing can be accomplished by to ways –
 Healing by first intention (primary union)
 Healing by second intention (secondary union)
 Healing by first intention (primary union): this is a wound which is
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Clean and uninfected
Surgically incised
Without much loss of tissue or cells
Edges of the wound are approximated by surgical sutures.
Healing by first intention (primary union)
Stages of primary healing:
1. Initial haemorrhage: Immediately after injury, the space is filled with
blood which then clots and seals the wound against dehydration and
infection.
2. Acute inflammatory response: Initially neutrophils appear at the site of
injury, which are replaced by macrophages by the 3rd day.
3. Epithelial changes: the basal cells of the epidermis proliferate from the
cut margins and migrate towards the incisional space. The migrating
epithelial cells separate the underlying normal connective tissue from
the overlying necrotic material and clot. A well approximated wound
gets covered by epithelium in 48 hrs.
Healing by first intention (primary union)
4. Organisation: by the 3rd day fibroblasts also invade the wound area. By
5th day, new collagen fibrils start forming, which continue to form till
healing is completed.
Suture tracks: each suture track is a separate wound and incites the same
phenomena as in healing of wounds.
If the sutures are removed after 1 week much of the epithelised track is
avulsed and the track is closed. Delay in removal of suture may lead to
complications.
Healing by second intention (secondary union)
 This happens in wounds which are
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Open with large tissue defect, may be infected
Having more loss of tissues and cells
Wound is not approximated by surgical sutures
Stages of secondary healing:
1. Initial haemorrhage
2. Inflammatory phase
3. Epithelial changes: epithelial cells proliferate from the edges and
close the defect but this takes more time as the area to be closed is
large and the epithelium does not fully cover the wound till
granulation tissue fills up the defect from below.
Healing by second intention (secondary union)
4. Granulation tissue: main bulk of the secondary healing is by formation
of the granulation tissue. It is named so because of the granular and
pink appearance of the tissue. Each granule corresponds to proliferation
of a new blood vessel.
Formation of granulation tissue involves proliferation of new blood vessels
(angiogenesis or neovascularisation), the new vessels when they are
newly formed are leaky but later become more stable. The second
important process taking place is formation of new fibers (fibrogenesis),
the newly formed blood vessels are seen in an amorphous ground
substance, which starts to get filled up by collagen fibers (6th day). This
changes the colour of the wound from red to pale pink.
Healing by second intention (secondary union)
5. Wound contraction: an important feature of this type of healing. Starts
after 2-3 days and continues till the 14th day. During this time the
wound is reduced in size.
this helps in rapid healing as the area of the injured tissue which has to
be replaced is less.
wound contraction takes place during granulation tissue formation.
Complications of wound healing
 1. Infection –delays wound healing
 2. Implantation
 3. Pigmentation
 4. Deficient scar formation
 5. Incisional hernia
 6. Hypertrophied scars and Keloid formation
 7. Excessive contraction
 8. Neoplasia
HEALING OF BONES – FRACTURE HEALING
 Bone fractures also heal by either primary union or secondary union.
 Primary union: occurs when there is approximation of fractured ends
by application of compression clamps. Healing takes place by formation
of medullary callus without formation of periosteal callus.
 Secondary union: this is the more common process. Involves three
main stages
 1. Procallus formation
 2. Osseous callus formation
 3. Remodelling
HEALING OF BONES – FRACTURE HEALING
 1. Procallus formation: the first step is haematoma formation, which
occurs due to bleeding from torn vessels. This is followed by
inflammatory response. Proliferation of mesenchymal cells from the
periosteum and endosteum leads to formation of granulation tissue.
this is known as soft tissue callus – it joins the two ends of the
fractured bone. Woven bone and cartilage start growing in this
granulation tissue.
A wider zone of the fractured bone is covered by woven bone and
cartilage, this helps in immobilising the fractured bone ends.
This stage is known as procallus formation and is divided into external
procallus, intermediate procallus and internal procallus.
HEALING OF BONES – FRACTURE HEALING
 2. Osseus callus formation: The procallus is invaded by new blood
vessels and ostoblasts, which replace the woven bone and cartilage with
lamellar bone.
 3. Remodelling: in this stage both osteoblastic and osteoclastic activity
is taking place. The external callus is cleared away, compact bone is
formed in place of intermediate callus and bone marrow cavity
develops in place of internal callus.