Correct Response: D. The stratum corneum is the outermost layer of skin and is part of the epidermis. The cells of the stratum corneum contain large quantities of keratin, a tough, fibrous protein that helps provide protective properties to the skin. Studies show that removal of the stratum corneum causes the skin to lose its ability to serve as a protective barrier. Collagen and elastic fibers within the skin's dermis provide strength and elasticity to skin (A). Eccrine sweat glands, also located in the dermis, release fluid that contains water and metabolic wastes (B). The release of sweat by eccrine sweat glands also helps dissipate heat (C).