Which vessel is the small branch of an artery that leads into capillaries?

• A. Arteriole
• B. Artery
• C. Capillary
• D. Vein

Answer: (A)

The main idea is how blood moves from arteries into the microcirculation. The small branch of an artery that leads into capillaries is an arteriole. Arterioles are the narrow, muscular vessels that come off arteries and feed into the capillary beds, where gas, nutrient, and waste exchange with tissues occurs. Their smooth muscle allows them to constrict or dilate, helping regulate blood flow and pressure before blood enters the capillaries. The other vessels have different roles: capillaries are the sites of exchange themselves, arteries are larger vessels that carry blood away from the heart, and veins return blood back toward the heart.