Which type of muscle is found in the walls of internal organs and helps move substances through the digestive and circulatory systems?

• A. Skeletal muscle
• B. Cardiac muscle
• C. Smooth muscle
• D. Diaphragm

Answer: (C)

The important concept here is that smooth muscle lines hollow organs and drives movement of contents without conscious control. Smooth muscle is found in the walls of internal organs like the stomach, intestines, blood vessels, and bladder. Its contractions are involuntary and non‑striated, meaning you don’t control them and they don’t show the banded appearance seen in other muscle types. These contractions propel food through the digestive tract (peristalsis) and help regulate blood flow by changing vessel diameter in the circulatory system. In contrast, skeletal muscle is voluntary and attached to bones for movement, cardiac muscle forms the heart walls and is specialized for pumping, and the diaphragm is a skeletal muscle involved in breathing. So, smooth muscle best fits the description.