What is the substance found in the stratum lucidum of the skin?

The stratum lucidum is a thin, clear layer of skin located just above the stratum granulosum and below the stratum corneum, primarily found in areas of thick skin such as the palms of the hands and soles of the feet. The primary substance found in this layer is eleidin, which is a translucent protein that is an intermediate form of keratin.

Eleidin plays a critical role in the process of keratinization, where cells progressively change as they move from deeper layers of the epidermis to the surface. Eleidin provides a temporary structure that helps to facilitate this transition, eventually leading to the formation of keratin within the stratum corneum. The presence of eleidin contributes to the thickness and protective quality of the skin in high-friction areas.

The other substances listed, such as keratin, melanin, and collagen, play essential roles in skin structure and function but are not specifically located in the stratum lucidum. Keratin is found in the stratum corneum and gives skin its toughness, melanin is responsible for pigmentation and is found in the epidermal layers, while collagen is primarily located in the dermis, providing strength and elasticity to the skin. Thus, eleidin is