Which muscle type constricts blood vessels?

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

Answer: (B)

Blood vessel constriction is carried out by smooth muscle in the walls of arteries and arterioles. This tissue is involuntary and non‑striated, organized in the tunica media, and when it contracts the vessel diameter narrows. That narrowing increases resistance and reduces blood flow, allowing the body to regulate blood pressure and direct blood where it’s needed. Skeletal muscle is attached to bones and voluntary, so it isn’t used to constrict vessels. Cardiac muscle makes up the heart and pumps blood, not constricting vessels. Striated muscle includes both skeletal and cardiac, but neither primarily constricts blood vessels. So the muscle type responsible for constricting blood vessels is smooth muscle.