Note a wound that might otherwise have healed by

Note: a wound that might otherwise have healed by primary intention may become
infected and heal by secondary intention.
Phases of healing:
 Inflammatory phase (begins at the time of injury and is a critical period because it
separates the wound environment for healing; it includes homeostasis and the vascular
and cellular phases of inflammation)
 Proliferative phase (primary process during this phase focus in the building of new tissue
to fill the wound space; the key cell during this phase is fibroblasts, these cells also
produce a family of growth factors that induce angiogenesis, endothelial cell
proliferation and migration)

 Wound contraction and remodeling phase (take place 3 weeks after the injury with the
development of the fibrous scar; there is a decrease in vascularity and continued
remodeling of scar tissue)
Two phases of scar formation:
 Emigration and proliferation of fibroblasts into the site of injury
 Deposition of ECM by these cells
Factors affecting wound healing:
 Malnutrition (adequate store of proteins, carbs, fats, vitamins, and minerals affect
wound healing; malnutrition slows the healing process causing wounds to heal
inadequate or incompletely)
 Blood flow and oxygen delivery (wounds must have an adequate blood flow to supply
the necessary nutrients and to remove the resulting waste, local toxins, bacteria, and
other debris; oxygen is required for collagen synthesis and killing of bacteria by
phagocytosis)
 Impaired inflammatory and immune response (inflammation is essential on the first
phase of wound healing and immune mechanisms prevent infections that impaired
wound healing)
 Infection, wound separation and foreign bodies
Chapter 15: Disorders of the immune response.
Hypersensitivity disorders (disorders caused by immune responses; are commonly classified into
four groups according to the type of immune response causing the injury and the mature and
location of the antigen that is target of the response)
 Type I immediate hypersensitivity disorders (IgE mediated reactions that begin rapidly,
often within minutes of an antigen challenge; referred to as allergic reactions and the
antigens are called allergens; according to the portal of entry these reactions may be
limited to merely annoying, severely debilitating, or systemic and potentially life-
threatening; systemic anaphylactic reaction is a life-threatening hypersensitivity reaction
characterized by widespread edema, difficulty breathing and vascular chock secondary
to vasodilation; local atopic reaction occur when the antigen is confined to a particular
site by virtue of exposure examples are allergic rhinitis and food allergy)
 Type II antibody-mediated disorders [mediated by IgG or IgM antibodies directed against
target antigens on cell surface or in connective tissue; three different antibody-mediated
mechanisms are involved:
 complement and antibody mediated cell destruction (occur because the cells are
coated with molecules that make them attractive to phagocytes or because of
the formation of membrane attack proteins that disrupt the integrity of the cell
membrane and cause cell lysis)