Inorganic matrix components include ions and minerals, water, and other minor components. The four basic tissues of the body, from which all organs are formed, are muscle, nervous, epithelial, and connective tissue. Each of these basic tissue types can be subdivided into more specific tissues types, but the basic tissue types perform strikingly different functions and appear quite different when viewed microscopically. Muscle tissue functions for movement of body parts, and has the unique ability of muscle cells, and hence muscle tissue, to contract 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 the majority of the heart, and pumps blood through the heart chambers.
Microscopically, muscle appears somewhat red in appearance and the cells are long and spindle shaped. Nervous tissue functions for electrical communication in the body. Neurons are the main nerve tissue cells, responsible for sending electrical signals along their cell processes, and propagating signals to other neurons by means of chemical signaling in the form of neurotransmitters. Neurons have a typical structure consisting of a cell body, or soma, long cell processes called axons, and dendritic extensions from the soma called dendrites. Supportive nerve tissue cells, called neuroglia, help nerve cells metabolically and immunologically.