Snapshot A 25-year-old African American woman presents to her dermatologist for a bothersome scar. She reports that a few months ago, she injured her arm after falling off a bike. Since then, her cut has healed and a raise flesh-colored scar has grown over the wound. It is often itchy or even painful. On physical exam, she has a 7 cm raised scar with irregular borders that extends beyond the original wound. (Keloid) Overview Skin is the largest organ of the body Functions photoprotection barrier formation homeostasis thermoregulation immunologic protection Skin is made of the epidermis and dermis Anatomy Epidermis layers from top to bottom stratum Corneum serves as a physiologic barrier from chemical and microbiologic invasion fluid and solute loss stratum Lucidum stratum Granulosum stratum Spinosum stratum Basale separates the epidermis and dermis “Californians Like Girls in String Bikinis” major cells keratinocytes mature from the stratum basale to the stratum corneum over the course of 4 weeks melanocytes produces melanin, which protects the skin from ultraviolet radiation Langerhan cells immune cells that present antigens Merkel cells contain neuroendocrine peptides Dermis layers from top to bottom papillary dermis reticular dermis functions as structural support and provides nutrition via the vasculature contains subdermal epithelial structures sebaceous glands apocrine glands hair follicles nerves Normal Wound Healing Wound disrupts structure and function of epidermis Activates keratinocytes, fibroblasts, endothelial cells, platelets, and macrophages Hemostasis and inflammatory phase (0-3 days) clot forms with platelet aggregation, trigger of clotting cascade, and small vessel constriction mast cells release histamine and other vasodilators to increase permeability in vasculature neutrophils and other inflammatory cells migrate into tissue edema or swelling is seen clinically macrophages clear debris Proliferative phase (3 days to weeks) fibroblasts deposits glycoprotein and mucopolysaccharides produce myofibroblasts myofibroblasts help to contract the wound to pull the edges together synthesize collagen (type III) the resulting collagen matrix stimulates angiogenesis keratinocytes re-epithelialize the wound the resulting collagen deposition and angiogenesis form granulation tissue abnormal wound healing in this phase deficiency in vitamin C or copper can result in delayed wound healing keloids and hypertrophic scars may result from persistent myofibroblasts or excessive matrix synthesis Remodeling (weeks to months) type III collagen is replaced by type I collagen, resulting in increased tensile strength of the tissue hypertrophic type 1 collagen deposition can result in formation of a contracture vessels mature remodeling is mediated by fibroblasts abnormal wound healing in this phase deficiency in zinc can result in delayed wound healing Wound Closure Intentions Primary intention wound edges are re-approximated faster healing and less scarring Secondary intention wounds are left open and allowed to granulate and fill in over time Tertiary intention (delayed closure) wounds are left open and observed wounds are then approximated and closed later