The skin + wound healing

• Skin

  Acts as a barrier to entry of infectious organisms
• Skin

  • Outer covering of body
  • Continuous at all natural openings
  • Functions: protects, regulation, sensation
• Skin protects from

  • Absorption of toxic substances
  • Radiation
  • Invasion of pathogens
• Skin regulates

  • Fluid
  • Vitamin D
• Physical challenges to skin integrity

  • Scratches
  • Pressure sores/ulcers
  • Puncture
• Thermal challenges to skin integrity

  • Burns
  • Frostbite
• Responses to trauma to skin

  • Defensive - inflammatory response, immune system
  • Reparative - renew surface barrier, may lead to scars
• Wound healing stages

  • Inflammatory phase - 2-5 days
  • Proliferative phase - 2 days - 3weeks
• Wound healing: Inflammatory phase

  Occurs immediately, 2-5 days
• Wound healing: Inflammatory phase - Haemostasis

  1. Vasoconstriction (epinephrine)

  2. Platelet aggregation (cytokine)

  3. Coagulation (liquid to gel)

  4. Clot formation
• Inflammatory phase - Haemostasis - Vasoconstriction

  • Damage to endothelium of blood vessels
  • Underlying collagen layer exposed
  • Attracts platelets
  • Liberate serotonin + vasoconstrictor agents
  • Vessel constricts
• Inflammatory phase - Haemostasis - Platelet aggregation

  • Formation of temporary plug of platelets
• Inflammatory phase - Haemostasis - Coagulation + clot formation

  1. Platelets bound together by fibroin

  2. Fibrinogen converted to fibrin in reactions

  3. Lack of clotting factor VIII = haemophilia

  4. Clotting inside blood cells = thrombosis
• Inflammatory phase - Stage B - Inflammation

  1. Vasodilation

  2. Phagocytosis
• Inflammatory phase - Stage B - Inflammation

  • Cleans wound of debris
  • Platelets release factors that attract WBCs
  • WBC remove debris from wound + release GF attracting fibroblasts from surrounding tissue
  • WBC ingested Hb from RBC, converts to other compound - gives colour of bruise
• Wound healing - Proliferative phase

  1. Granulation

  2. Contraction

  3. Epithelialisation
• Proliferative stage - Granulation

  • Fibroblasts synthesise collagen
  • Cavity filled by newly formed tissue
  • Granulation tissue = leucocytes, fibroblasts, vascular endothelial cells
• Proliferative stage - Contraction

  • Immune cells & exudate migrate outwards into wound forming puss in wound cavity
  • Provides outward irrigating fluid & anti-bacterial substance carry away bacteria
  • Tissue grows up till cavity is filled
• Proliferative stage - Epithelialisation

  • New epithelium crosses moist surface
  • Epithelium grows out over granulation tissue to re-establish continuity of skin
  • Collagen fibres start fine but turn coarse, strengthen and shorten over time, cause puckering of scar
• Wound healing - Maturation or remodelling phase

  Occurs 3 weeks to 2 years
• Maturation or remodelling phase

  • New collagen forms to increase tensile strength
  • Scar tissue only 80% as strong as original tissue
• Deeper cuts & wounds - Assisted wound healing steps

  1. Apply pressure

  2. Use cold water

  3. Cover with ointment

  4. Chemicals as topical agents

  5. Stitch, suture, staple, glue