What is the classification of muscles that are involuntary and found in internal organs?

Smooth muscle is classified as involuntary muscle tissue, which means it operates without conscious control. It is primarily found in the walls of internal organs such as the intestines, bladder, and blood vessels. The smooth muscle's structure is non-striated, allowing it to contract in a slower and more sustained manner compared to other muscle types. This feature is particularly important for functions like moving food through the digestive tract, regulating blood flow, and controlling bladder function.

In contrast, skeletal muscle, which is striated and under voluntary control, is responsible for moving bones and facilitating body movements. Cardiac muscle, while also involuntary, is specifically found in the heart and has a distinct structure and function compared to smooth muscle. Striated muscle is a term that encompasses both skeletal and cardiac muscle, highlighting the patterned appearance created by the arrangement of muscle fibers. Thus, smooth muscle is the correct classification in this context.