In animals, such as vertebrates, the epidermis is made up of four or five layers (each called stratum). These layers protect the underneath layers of the skin against physical damage, infection, and water loss. In humans, the epidermis consists of the following layers: (1) stratum corneum, (2) stratum lucidum, (3) stratum granulosum, (4) stratum spinosum, and (5) stratum basale or germinativum).
The stratum lucidum is a Latin term, which literally means clear layer. The name is derived from its translucence when viewed under a microscope. This layer is found particularly in the palmar and plantar skin. The presence of the stratum lucidum makes the palmar and plantar skin characteristically thick. The skin in other body parts lacks stratum lucidum. Its presence indicates the importance of having thicker skin to protect against frequent exposure to mechanical stress.
- clear layer of the epidermis