The term 'OUTER SURFACES' can be summed up in one word: SKINS. The term 'SKINS' refers to the outermost layer of an organism, which is composed of cells and provides protection from the environment. It also serves as a barrier to prevent the loss of water and other substances. In humans, the skin is the largest organ and is composed of several layers, including the epidermis, dermis, and subcutaneous tissue.