epithelia

tissue made up of cells packed closely together and bound by connective material. It covers the outer surface of the body and lines vessels and organs in the body. One surface is fixed to a basement membrane and the other is free, and it provides a barrier against injury, microorganisms and some fluid loss. There are various types of epithelium in single and multiple (or stratified) layers and differing shapes, namely, cuboidal, squamous (like flat pads) and columnar. The shape suits the function, so the SKIN is formed from stratified squamous (and KERATINIZED ) epithelium while columnar epithelia, which can secrete solutions and absorb nutrients, line the INTESTINES and stomach.