Which type of muscle is located in the walls of organs and arteries and is not under voluntary control?

• A. Smooth muscle
• B. Cardiac muscle
• C. Skeletal muscle
• D. Tendon tissue

Answer: (A)

Muscles that work automatically in the walls of hollow organs and blood vessels are smooth muscle. This type is not under conscious control; it’s regulated by the autonomic nervous system and hormones, causing slow, sustained contractions that move contents through organs (like peristalsis in the GI tract) and adjust vessel diameter.

Smooth muscle fibers are non‑striated and spindle-shaped, which distinguishes them from other muscle types. In contrast, cardiac muscle, while also involuntary, is located in the heart and is striated with intercalated discs, designed for rhythmic pumping. Skeletal muscle is voluntary, striated, and attached to bones, enabling deliberate movements. Tendon tissue isn’t muscle at all; it’s connective tissue that connects muscle to bone.