Tissue

Tissue, in biology, similar cells grouped together in multicellular animals and plants. These cells are usually specialized for a single function; thus muscle cells contract but do not secrete, and nerve cells conduct impulses but have little or no powers of contraction. The cells are held together by intercellular material. Having become specialized for a single or at most a very narrow range of functions, they are dependent upon other parts of the organism for necessities like food and oxygen. Groups of tissues, each with its own functions, make up organs. Connective tissue refers to the material in which all the specialized body organs are embedded and supported.