ABSTRACT
Through our skin we are able to touch our environment. But the skin has functions that go far beyond sensory perception. It prevents us from drying out, protects us against abrasion, and imposes a physical barrier against
disease-causing agents. In addition, Langerhans' cells, members of the immune system, survey our skin and play an active role in cell-mediated immunity, protecting us from invasion by foreign organisms. By the time we are adults, our skin is made up of two principal components, the epidermis and the dermis (Fig. 12-1).
