<P> Muscle cells form the active contractile tissue of the body known as muscle tissue or muscular tissue . Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs . Muscle tissue is separated into three distinct categories: visceral or smooth muscle, found in the inner linings of organs; skeletal muscle, typically attached to bones, which generate gross movement; and cardiac muscle, found in the heart where it contracts to pump blood throughout an organism . </P> <P> Cells comprising the central nervous system and peripheral nervous system are classified as nervous (or neural) tissue . In the central nervous system, neural tissues form the brain and spinal cord . In the peripheral nervous system, neural tissues forms the cranial nerves and spinal nerves, inclusive of the motor neurons . </P> <P> The epithelial tissues are formed by cells that cover the organ surfaces such as the surface of skin, the airways, the reproductive tract, and the inner lining of the digestive tract . The cells comprising an epithelial layer are linked via semi-permeable, tight junctions; hence, this tissue provides a barrier between the external environment and the organ it covers . In addition to this protective function, epithelial tissue may also be specialized to function in secretion, excretion and absorption . Epithelial tissue helps to protect organs from microorganisms, injury, and fluid loss . </P> <P> Functions of epithelial tissue: </P>

Example of a tissue found in the human digestive system