Repair

1
Repair

• Dr. Gehan Mohamed Dr. Abdelaty Shawky
  

2
Intended Learning outcomes

• Understanding the classification of human cells
  according to their ability for proliferation.
• Identifying the types of repair.
• Discussing the mechanism of wound healing.
• Recognizing the complications of wound healing.
• Understanding the process of healing of bone
  fracture.
• Being oriented with the factors affecting the
  process of repair.

3
Types of cells according to the ability of cell
proliferation

• 1. Labile cells are Conteniously dividing cells
  and renew themselves e.g skin epithelium
  ,mucosal lining of the GIT, haematopoietic cells
  (blood cells ).
• 2. Quiescent cells (Stable) cells divide when
  there is a need e.g hepatic, kidney and pancreas
  .
• 3. Permanent cells Non-dividing cells so when
  injured heal by fibrous tissue e.g nerve cells
  and skeletal, cardiac muscle cells

4
Repair (Healing)

• Definition Replacement of damaged tissue with
  new healthy living tissue.
• Types
• A. Regeneration
• healing by the same type of tissue cells from
  surrounding healthy living cells, this occurs
  with small damages of labile cells and stable
  cells for examples liver cirrhosis and bone
  fractures
• B. Fibrosis (scar tissue)
• healing by granulation tissue (fibroblast with
  new capillaries) which mature to hypovascular
  fibrous tissue (scar), this occurs in the healing
  process of permanent cells or in stable cells
  with high damage. for example myocardial
  infraction and wounds

5
Wound Healing

• Cutaneous wound healing is generally divided into
  four phases
• Homeostasis.
• Inflammation.
• Granulation tissue formation and
  Re-epithelialization
• Remodeling.
• - Wound healing is a fibroproliferative response
  that is mediated through growth factors and
  cytokines.

6
1. Homeostasis

• Immediately after injury the cut vessels bleed
  inside the wound defect to form a blood clot that
  unit the two cut ends temporarily.
• Vasoconstriction of the injured vessels at the
  edges of the wound followed by platelets
  aggregation and adherence to the damaged
  endothelium.
• Stimulation of coagulation system will form
  fibrin.
• Fibrin network is formed over the aggregated
  platelets to form a 1ry homeostatic plug that
  stops bleeding inside the wound.

7

• 2. Inflammation
• Mediated by polymorphs and macrophages.
• Within the first 6-8 hours, the
  polymorphonuclear leukocytes (PMNs) kill any
  organism in the wound and liquefy any necrotic
  debris.
• As the process continues, monocytes also exude
  from the blood vessels. These are termed
  macrophages. The macrophages continue and engulf
  the necrotic debris and also manufacture various
  growth factors during days 3-4.

8

• 3. Granulation tissue formation and
  re-epithelization
• In days 5-7, fibroblasts migrate into the wound,
  laying down new collagen of the subtypes I and
  III
• Angiogenesis is the formation of new capillaries
  from the healthy blood vessels at the edge of the
  wound. These new capillaries fill the wound
  defect and surrounded by fibroblasts.
• The newly formed capillaries fibroblasts
  granulation tissue.
• Re-epithelization occurs by proliferation and
  migration of the healthy epidermal cells from the
  edges of the wound inwards.

9
Granulation tissue
10
Granulation tissue
Epithelization
capillary
fibroblast
11

• 4. Remodeling
• - After the third week, the wound undergoes
  constant alterations, known as remodeling.
• Collagen is deposited from fibroblasts and
  degraded by collagenase enzyme which secreted
  from macrophages in a controlled manner.
• Wound contraction is a process occurs by the
  action of myofibroblasts (modified fibrobalsts),
  which resemble contractile smooth muscle cells.
  This occurs to give the healing wound more
  strength.

12
Types of wound healing

• 1. Healing by primary union (first intention)
• - Occurs with clean, non-gaping wounds (stitched
  surgical incision).
• 2. Healing by secondary union (secondary
  intention)
• - Occurs with extensive tissue loss as in large
  wounds, infected wounds, abscess, ulcers.etc.

13
(No Transcript)
14
Complications of the healing process

• A. Complications from deficient granulation
  tissue formation
• 1. Ulcers discontinuity of the covering
  epithelium or mucous membrane .
• 2. Sinus is blind end track of septic
  granulation tissue connecting a cavity to the
  outside e.g. pilonidal sinus
• 3. Fistula is a tract of septic granulation
  tissue connecting 2 epithelial surfaces e.g.
  perianal fistula.
• 4. Weak atrophic scar this may lead to hernia .

15

• B. Complications due to excessive granulation
  tissue formation
• 1. Hypertrophied scar.
• 2. Keloid formation if the formed scar
  exceeded the original size of the wound.

16
Keloid
Hypertrophic scar
17
Keloid
B
A
18

• C. Other complications
• Infection leading to delayed healing
• Squamous cell carcinoma rarely scars may develop
  
• Cicatrisation contracture of the size of the
  scar
• Implantation epidermiod cyst is a cyst formed
  secondary to entrapment of part of the epithelium
  inside dermis.
• Stump neuroma following amputation causing a
  painful coiled mass of nerves

19
Bone Fracture

• TYPES
• Simple.
• Compound .
• Comminuted fracture into pieces.
• Greenstick is a partial fracture involve only
  one side of bone , common in children.

20
Types of Fracture
21
Mechanism of healing of bone fracture
22
Complications of bone fracture

• 1. Delayed union (healing) due to old age,
  anaemia, calcium or vitamin D deficiency
• 2. Non union due to soft tissue interposition
  between the two fracture ends.
• 4. Mal union of healed bones due to improper
  reduction.
• 5. Bone necrosis due to injury to nutrient
  artery.

23
Factors affecting Repair

• I. Local factors
• The type of the damaged cells ( labile, stable or
  permanent).
• Severity of the damage.
• Presence of foreign body.
• Presence of necrotic tissue.
• Infection.
• Irradiation.
• Blood supply.

24

• II. General factors
• Age of patient.
• Nutrition status.
• Diseases Diabetes, malignancy, anaemia.
• Drugs Corticosteroid therapy, chemotherapy..