What are the key differences in the structure and function of smooth muscle compared to cardiac muscle?

Smooth muscle and cardiac muscle have different structures and functions. Smooth muscle is found in organs like the intestines and blood vessels, and is involuntary. It has a spindle-shaped structure and contracts slowly and rhythmically. On the other hand, cardiac muscle is found in the heart and is also involuntary. It has a branching structure and contracts quickly and continuously to pump blood throughout the body.