The stratum lucidum (Latin for "clear layer") is a thin, clear layer of dead skin cells in the epidermis named for its translucent appearance under a microscope. It is readily visible by light microscopy only in areas of thick skin, which are found on the palms of the hands and the soles of the feet.
Located between the stratum granulosum and stratum corneum layers, it is composed of three to five layers of dead, flattened keratinocytes. The keratinocytes of the stratum lucidum do not feature distinct boundaries and are filled with eleidin, an intermediate form of keratin.
The thickness of the lucidum is controlled by the rate of mitosis (division) of the epidermal cells. In addition, melanocytes determine the darkness of the stratum lucidum. The cells of the stratum lucidum are flattened. They are surrounded by an oily substance that is the result of the exocytosis of lamellar bodies accumulated while the keratinocytes are moving through the stratum spinosum and stratum granulosum.
Famous quotes containing the word stratum:
“If you chance to live and move and have your being in that thin stratum in which the events that make the news transpire,—thinner than the paper on which it is printed,—then these things will fill the world for you; but if you soar above or dive below that plane, you cannot remember nor be reminded of them.”
—Henry David Thoreau (1817–1862)