The smooth muscle surrounding the other hollow organs is involuntary, meaning it does not need to be told to contract. So functionally, cardiac muscle and smooth muscle are similar. Anatomically though, cardiac muscle more closely resembles skeletal muscle. Both skeletal muscle and cardiac muscle are striated. Under medium to high power magnification through the microscope, you can see small stripes running crosswise in both types.
Smooth muscle is nonstriated.
Cardiac muscle could almost be said to be a hybrid between skeletal and smooth muscle. Cardiac muscle does have several unique features. Present in cardiac muscle are intercalated discs, which are connections between two adjacent cardiac cells. Intercalated discs help multiple cardiac muscle cells contract rapidly as a unit. This is important for the heart to function properly.