Development of the Epidermal Barrier

After completing this article, readers should be able to: 1. Name the four epidermal strata. 2. List the epidermal stratum that is primarily deficient in the very low-birthweight preterm infant and its primary function. 3. Characterize the physiologic similarities between the developing skin and the developing lung. 4. Describe the only nonectodermal cell in the epidermis, its derivations, and its functions in the innate immune system. 5. List the physiologic mechanisms contributing to epidermal barrier formation. Problems related to the epidermal barrier are particularly acute in the very low-birthweight (VLBW) population. Approximately 500,000 preterm infants are born each year in the United States. (1) The survival and long-term outcomes of these infants are directly proportional to their maturity and weight at birth. Preterm infants account for 74% of neonatal deaths. Those born before 28 weeks of gestation account for 50% of neonatal deaths. (1) This vulnerable population possesses an absent or incompetent epidermal barrier. (2) Such infants have problems with temperature control and infection and an increased likelihood of damage from adhesives and superficial trauma. A better understanding of the ontogeny of the epidermal barrier is critical to developing evidence-based guidelines for infant skin care and neonatal care practices. Skin care practices affecting VLBW infants include bathing/cleansing, thermoregulation, acid mantle formation, blood drawing, care of central venous catheters, and adhesion of tapes. The scientific basis for such practices is grounded in an understanding of the biochemistry and development of the epidermal barrier. The skin is a complex, multifunctional organ that forms the interface between the organism and the environment (Fig. 1⇓ ). The bulk of the skin is composed of the dermis and consists of collagen embedded in a hydrated matrix of glycosaminoglycans. Blood vessels and the vast majority of cutaneous nerve endings are present in the dermis. The cells of the dermis and …