Involuntary muscle found inside many internal organs, such as the digestive system, are ____ muscles.

Involuntary muscle found inside many internal organs, such as the digestive system, are ____ muscles.

• A. Cardiac Muscle
• B. Smooth Muscle
• C. Voluntary Muscle
• D. Skeletal Muscle

Answer: (B)

Smooth muscle forms the walls of hollow internal organs, including the digestive tract. These muscles contract in a slow, wave-like way to move contents along the gut (peristalsis) and to mix substances, and they operate without conscious control. Under the microscope they are non-striated and spindle-shaped, reflecting their unique organization compared with other muscle types. They are controlled by the autonomic nervous system and local factors, not by voluntary effort. By contrast, skeletal muscle is voluntary and attached to bones (striated and organized for quick, forceful movements), while cardiac muscle is involuntary but located in the heart (also striated and structurally specialized). Therefore, the description matches smooth muscle.

Smooth muscle forms the walls of hollow internal organs, including the digestive tract. These muscles contract in a slow, wave-like way to move contents along the gut (peristalsis) and to mix substances, and they operate without conscious control. Under the microscope they are non-striated and spindle-shaped, reflecting their unique organization compared with other muscle types. They are controlled by the autonomic nervous system and local factors, not by voluntary effort. By contrast, skeletal muscle is voluntary and attached to bones (striated and organized for quick, forceful movements), while cardiac muscle is involuntary but located in the heart (also striated and structurally specialized). Therefore, the description matches smooth muscle.