American Academy of Professional Coders (AAPC) Practice Exam

Which type of muscle aids in digestion and is involuntary?

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

4. Striated muscle

The correct answer is: Smooth muscle

Smooth muscle is the correct answer as it plays a crucial role in digestion and operates involuntarily, meaning it functions without conscious control. This type of muscle is found in the walls of hollow organs, particularly in the digestive tract, where it facilitates peristalsis—the rhythmic contractions that push food through the esophagus, stomach, and intestines. Unlike skeletal muscle, which is under voluntary control and associated with movement of the skeleton, or cardiac muscle, which is also involuntary but specific to the heart, smooth muscle is essential for regulating processes within internal organs. Striated muscle refers to muscle that has a striped appearance, typical of skeletal and cardiac muscle, but does not apply to the smooth muscle involved in digestion. Therefore, smooth muscle's unique characteristics make it integral to the digestive process and highlight its involuntary nature.