Final answer:
Smooth muscle is the type of muscle that aids in digestion, by contracting involuntarily to move food through the digestive system.
Step-by-step explanation:
The type of muscle that aids in the digestion of food is smooth muscle. This muscle tissue is found in the walls of internal organs such as the stomach and intestines. By contracting rhythmically, smooth muscle propels food through the digestive tract, a process known as peristalsis. Unlike skeletal muscles, which are involved in voluntary movements like walking, smooth muscles operate involuntarily under the control of the autonomic nervous system. Cardiac muscle is specific to the heart and is involved in pumping blood. Finally, skeletal muscles, which are also called voluntary muscles, move the skeleton and facial muscles are part of this group, but they are not directly involved in digestion.