Final answer:
The stratum lucidum is a transparent protective layer in the thick skin of palms, soles, and digits, rich in eleidin protein that helps prevent water loss. Found between the stratum granulosum and stratum corneum, it features dead, flattened keratinocytes that contribute to its translucent appearance.
Step-by-step explanation:
The stratum lucidum is a distinctive layer of the epidermis, specifically found in the thick skin of body areas such as the palms of the hands, soles of the feet, and digits. It resides just above the stratum granulosum and below the stratum corneum. The primary function of this layer is to provide a barrier to water loss and enhance the skin's protective qualities against external damage. Keratinocytes, the main type of cells in this layer, are loaded with a clear, lipid-rich protein called eleidin, which is a derivative of keratohyalin. Eleidin is responsible for the transparent appearance of the stratum lucidum and plays a crucial role in the skin's barrier function.
The stratum lucidum acts as an additional layer of protection for areas of skin that encounter frequent friction or pressure. The keratinocytes here are dead and flattened, contributing to the translucency of this layer. This feature, along with its location in the epidermis, gives the stratum lucidum its name, which means 'light' or 'transparent' layer. The presence of eleidin helps to prevent water loss through the epidermis, grounding it as an essential part of the body's moisture retention and protective strategies.