The stratum lucidum is the next layer up. This is the layer only seen on the thick skin of the hands and feet. These cells are flat and dead; they are packed with eleidin, which is a lipidladen clear protein that makes this layer relatively translucent. This protein gives this layer the ability to repel water. The stratum corneum is the most superficial layer in the epidermis. The keratinization of these cells is significant and there are 15-30 layers in this part of the epidermis. The cells are dead and dry; they prevent penetration of pathogens (microbes) and prevent the dehydration of the rest of the skin. The stratum granulosum or the stratum lucidum replace these cells, which are completely turned over after four weeks.
THE DERMIS The dermis is between the epidermis and the hypodermis. The dermis is vascularized, containing blood vessels, nerves, lymph vessels and accessory structures of the skin, such as the sweat glands and hair follicles. There are two layers to the dermis, made from the interconnection and weaving of collagen and elastin fibers—each of which is made by fibroblast cells. Figure 26 shows what the dermis looks like, including the structures within it:
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