The stratum lucidum is layer of dead skin cells within the epidermis. The epidermis, or outer layer of skin, is present throughout the human body, but the stratum lucidum is present only where the skin is especially thick, such as the soles of the feet and the palms of the hands. This layer, which is designed to help the body handle friction, is transparent when viewed under a microscope.
Within the epidermis, the stratum lucidum lies between the layers called the stratum corneum and the stratum granulosum. The stratum corneum makes up the outer layer of the epidermis and contains dead skin cells. This is the portion of the skin that is responsible for the skin's ability to stretch. The stratum granulosum is also known as the granular layer of the skin. This layer contains a protein that is responsible for the breakdown of skin cells.
The stratum lucidum is an important layer of the skin because it provides several types of protection. Its thickness reduces the effects of friction, particularly in areas prone to these effects, such as the palms and soles. This layer also causes the skin to be waterproof, which is why it is often called the barrier layer of skin.
Consists of Layers of Keratinocytes
There are three to five layers of keratinocytes that make up the stratum lucidum. Keratinocytes are the primary cells that make up the epidermis, and they are often referred to as basal cells. These cells are responsible for forming a layer of keratin that will assist in the breakdown of skin cells so that the body can shed these old cells in favor of new skin cells. Keratinocytes also help to protect the human body from ultraviolet radiation.
The keratinocytes found in the stratum lucidum are flat and do not contain any noticeable boundaries. The insides of these cells contain a type of oily substance that is believed to be made as a result of lysosome disintegration. Lysosomes are the structures responsible for creating enzymes that ultimately destroy old cells so new ones can grow, thus regenerating the tissues of the body.
The keratin formed by the keratinocytes are proteins found in the epidermis. This protein is also found in fingernails, toenails and hair. In animals, keratin also forms hooves and horns. The type of transformed keratin found in the stratum lucidum is known as eleidin. This substance is made of small granules and is found in the protoplasm part of cells.