23. Phases of wound healing (also beginning and duration of each phase)

Question 1

23. Phases of wound healing (also beginning and duration of each phase)

Answer 1

Wound healing
-four distinctive phases
>acute inflammatory phase
>debridement phase(breakdown)
>proliferation phase(reparation)
>maturation phase(remodelling)
-depending on the type of wound and its classification,one or several
phases of wound healing can be accelerated,delayed or complicated
-several phases at the same time

Inflammatory phase
-characterized by (5):redness,pain,heat,swelling,loss of function
-lasts approximately 5 days
-after wounding:
1.filling with blood and lymph(from damaged vessels)
2.immediate vasoconstriction of the damaged vessels(lasts 5-10 min)
3.vasodilation(dilutes toxic substances,provides nutrients and results in blood clot)
4.epithelial cells begin to migrate from the wound periphery onto the
exposed tissue
5.the blood clot dries to form a scab(rupi)
6.white blood cells leaking into wounds initiate the debridement phase

Debridement phase
-approximately 6-12 hours after injury
-formed inflammatory exudate provides all the necessary phagocytic
cells and proteolytic enzymes to deal with the demarcation
-an exudate(of WBC,dead tissue,wound fluid)forms on the wound
-necrotic tissue impedes wound healing
-phase ends with the rejection of nonvital tissue
-sometimes combined with inflammatory phase

Proliferation phase
-repair phase
-approximately 3-5 days after injury
-signs of inflammation subside
-neovascularization
-divided into 3 processes:
>granulation
>wound contraction
>epithelialization

Proliferation phase(granulation)
-red irregular surface
-fragile tissue
-functions as a barrier to infection and a scaffold for migrating epithelial cells
-capillary network occurs through sprout formation of capillary endothelial cells on the wound surface
-granulation tissue formed at each wound edge at a rate of 0.4 to 1
mm/24h

Proliferation phase(wound contraction)
-the surface and the cavity of the wound become smaller
-adjacent skin pulled closer to the centre of the wound
-especially loose skin
-begins 5-9 days after wounding
-stops when edges connected/tension too high
-risk of contracture
-thinning of the surrounding skin(temporary)

Proliferation phase(epithelialization)
-proliferation of basal epithelial cells from the adjacent skin edges and
their moving over and adhesion to the surface of the wound
-prevention of excessive formation of granulation tissue
-total duration can range from days to weeks
-surface of the wound that has become epithelialized is known as the
epithelial scar(thin and fragile)

Maturation phase
-increasing strength of the scar as a result of remodelling of tissue
-the newly formed collagen is arranged parallel to the tension lines of the skin
-total duration can range from weeks to a year or even longer
-no or insufficient hair follicles,sweat and sebaceous glands,poor
movability and elasticity and an absence of pigment
-the healed wound will never regain skin’s original strength

Acute vs chronic wounds
-in chronic wounds there is a lack of orderly progression through the
four phases of wound healing
-an important cause of chronic wounds is infection, which causes a
sustained inflammatory phase
-factors influencing wound healing:
>malnutrition
>radiation
>use of corticosteroids
>underlying metabolic diseases