What is the cause of the striated appearance of skeletal and cardiac muscle?

the longitudinal position of muscle fibers gives the striated appearance in skeletal and cardiac muscle.

Explanation:

The striated appearance in skeletal and cardiac muscles is given by the longitudinal and paralele orientation of the muscle fibers. This can be appreciated with a microscope. Smooth muscles have a different distribution of their fibers that gives the impression of smoothness when observed with a microscope.