Which muscle tissue is involuntary and found in the walls of internal organs?

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

Answer: (B)

Smooth muscle tissue is involuntary and forms the walls of hollow organs and vessels. Its cells are spindle-shaped and non-striated, and it contracts under autonomic control, producing slow, sustained movements such as peristalsis in the digestive tract and vasoconstriction in blood vessels. This distinguishes it from skeletal muscle, which is voluntary and striped, and from cardiac muscle, which is involuntary but also striped and located in the heart. Because the description specifies muscle in the walls of internal organs, smooth muscle is the correct tissue.