Final answer:
The epidermis consists of several layers of cells, including the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only on the palms and soles), and stratum corneum. The innermost layer contains stem cells that divide to form new keratinocytes, while the outermost layer is made up of flat, dead, tightly packed keratinocytes that form a tough, waterproof barrier. Keratinocytes are cells that manufacture and store the protein keratin, giving hair, nails, and skin their hardness and water-resistant properties.
Step-by-step explanation:
The epidermis is composed of several layers of cells. The innermost layer, called the stratum basale, contains stem cells that divide to form new keratinocytes. The next layer, the stratum spinosum, is the thickest layer and contains Langerhans cells and spiny keratinocytes. This is followed by the stratum granulosum, in which keratinocytes are filling with keratin and starting to die. The stratum lucidum is only found on the palms and soles, and consists of translucent dead keratinocytes. The outermost layer is the stratum corneum, which consists of flat, dead, tightly packed keratinocytes that form a tough, waterproof barrier for the rest of the epidermis.
The cells in all of the layers except the stratum basale are called keratinocytes. These cells manufacture and store the protein keratin, which gives hair, nails, and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers.