Inorganic matrix components include ionsand minerals, water, and other minor components. The four basic tissues of the body, fromwhich all organs are formed, are muscle, nervous, epithelial, and connectivetissue. Each of these basic tissue types can be subdivided into more specifictissues types, but the basic tissue types perform strikingly differentfunctions and appear quite different when viewed microscopically. Muscle tissue functions for movement of bodyparts, and has the unique ability of muscle cells, and hence muscle tissue, tocontract or shorten. Smooth muscle is found in the walls of internal organs such as vessels,stomach, pancreas, bronchiole airways, and so on.
Cardiac muscle forms themajority of the heart, and pumps blood through the heart chambers.
Microscopically, muscle appears somewhat red in appearance and the cells arelong and spindle shaped. Nervous tissue functions for electricalcommunication in the body. Neurons are the main nerve tissue cells, responsiblefor sending electrical signals along their cell processes, and propagatingsignals to other neurons by means of chemical signaling in the form ofneurotransmitters. Neurons have a typical structure consisting of a cell body,or soma, long cell processes called axons, and dendritic extensions from thesoma called dendrites. Supportive nerve tissue cells, calledneuroglia, help nerve cells metabolically and immunologically.