Axons are the main projections of nerve cells that transmit signals. Schwann cells (a type of glial cell) form the myelin sheath around axons in the peripheral nervous system. Connective tissues (epineurium, perineurium, endoneurium) form the outer layers and internal support structure of nerves. Smooth muscles are a type of muscle tissue found in organs and blood vessels; they are not structural components of a nerve. While nerves innervate smooth muscles (control their function), the muscle tissue itself is not part of the nerve structure.