Wound Care

Principles of Skin and Wound Care 41
These cells produce a superoxide that fights
bacteria and enhances the effect of antibiotics. If the
bacterial count is high, so is the neutrophil count and
the amount of time the neutrophils stay in the wound
will be prolonged. The neutrophil is the primary cell
responsible for cleansing the wound of microorganisms
and a lack of significant numbers of neutrophils
will retard wound healing. In approximately 4 days
after the injury, macrophages arrive and gradually
replace the PMNs. These cells function in a low-oxygen,
high-acidotic environment to phagocytize debris
and control infection by microorganism ingestion and
excretion of ascorbic acid, hydrogen peroxide, and lactic
acid. It is the macrophage (derived from the monocyte)
that assumes the “director” role from this point
forward in the wound healing process. Macrophages
secrete angiogenesis growth factor (AGF), which stimulates
the budding of endothelial cells for initiation of
neoangiogenesis (new blood vessel formation).
Additionally, the macrophages control various processes
in wound healing and convert macromolecules into
amino acids and sugars needed for healing. They also
secrete lactate to stimulate collagen synthesis.
• Macrophages in combination with dead platelets
produce fibroblast-stimulating factor which signals
the fibroblasts to migrate during the last stage of the
inflammatory phase. Fibroblasts are the cells that
build the matrix of collagen during the proliferative
phase. At this phase they begin to differentiate and
some become myofibroblasts during the later stage
of inflammation. The myofibroblasts have the
ability to expand and contract thereby drawing the
wound together and influencing the rate and
amount of wound contraction.
• The macrophage is thought to live months to years
and remains in the wound fluid during all phases of
healing.