Principles of Wound Healing

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What are the layers of skin?

The epidermis and dermis are the two main layers of skin. The epidermis is further separated into the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale (from superficial to deep). The layers of the dermis include the papillary and reticular dermis.

2

What is a scar?

A scar is an area of fibrosis that replaces normal skin after injury. A scar always forms after an injury, as it is the product of a normal wound healing process. Scars can be made less visible with various surgical and nonsurgical techniques.

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What is healing by primary intention?

Healing by primary intention healing occurs when the edges of the wound are brought together in direct contact, which may involve sutures, staples, or other closure methods. This is the most commonly used method of wound closure and results in a minimally visible surgical scar.

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What is healing by secondary intention? ( Fig. 59.1 )

Healing by secondary intention occurs when wound edges are not approximated, leaving an area of exposed subcutaneous tissue. This may result in greater wound contracture than seen in primary closure. This type of healing works best in concavities (e.g., temporal fossa, medial canthus, alar groove). It can be useful in scalp and forehead wounds. Advantages include low risk of infection, high rate of healing, acceptable cosmesis, and surveillance in cases where cancer may be incompletely excised.

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What is healing by tertiary intention?

Healing by tertiary intention is delayed primary closure. Wound edges are not closed immediately, but the defect is allowed to undergo the acute inflammatory phase in which phagocytosis of contaminated tissue occurs and the microbial count decreases. The wound edges are then brought together and closed.

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What are the three phases of surgical wound healing?

• 1.

  Inflammatory phase (injury to approximately 1 week)

• 2.

  Proliferative phase (30 minutes to approximately 1 month)

• 3.

  Remodeling phase (3 weeks to approximately 1 year)

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What occurs in a wound during the inflammatory phase?

Local vasoconstriction occurs within the first 5 to 10 minutes and, then the coagulation cascade proceeds and a fibrin clot is formed. Activated platelets release several chemotactic factors that affect vascular tone. Vasodilation subsequently ensues secondary to histamine release. Next, the cellular response begins. Macrophage, neutrophil, and lymphocyte infiltration occurs, hallmarking the inflammatory phase. Importantly, only when inflammation subsides does collagen deposition begin. Therefore wounds with excess nonviable debris will experience a prolonged inflammatory phase.

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