Which statement correctly describes smooth muscle?

• A. Voluntary muscle that moves the skeleton.
• B. Non-striated cardiac muscle.
• C. Involuntary muscle found inside many internal organs.
• D. Muscle responsible for posture only.

Answer: (C)

Smooth muscle is the type of muscle that works automatically, without conscious control, and it has no obvious stripes when viewed under a microscope. It forms the walls of hollow organs and structures such as the stomach, intestines, blood vessels, airways, bladder, and uterus. Its contractions are slow and sustained, helping to move contents along the digestive tract (peristalsis), regulate blood flow by changing vessel diameter, and control the flow of air and urine. This activity is governed by the autonomic nervous system and local chemical signals, not by voluntary motor commands. It’s distinct from skeletal muscle, which is voluntary and moves the skeleton, and from cardiac muscle, which is striated and located in the heart. Smooth muscle is not primarily for posture; its main role is to manage internal organs and vessels.