Which vessel is the smallest branch of the arterial system that contains smooth muscle?

Which vessel is the smallest branch of the arterial system that contains smooth muscle?

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

Answer: (A)

Arterioles are the smallest arterial branches that still contain smooth muscle in their walls. As the arteries branch, they become progressively smaller, and the smooth muscle in the tunica media of arterioles allows them to constrict or dilate. This control of vessel diameter regulates blood flow into the capillary beds and helps manage systemic vascular resistance and blood pressure. Capillaries are the sites of exchange and are essentially just endothelial tubes, sometimes with pericytes, but they do not have a muscular layer. Veins carry blood back to the heart and have thinner walls with less smooth muscle. The aorta is a large artery with a substantial muscular and elastic wall but is not the smallest arterial branch. So the vessel described is the arteriole.

Arterioles are the smallest arterial branches that still contain smooth muscle in their walls. As the arteries branch, they become progressively smaller, and the smooth muscle in the tunica media of arterioles allows them to constrict or dilate. This control of vessel diameter regulates blood flow into the capillary beds and helps manage systemic vascular resistance and blood pressure.

Capillaries are the sites of exchange and are essentially just endothelial tubes, sometimes with pericytes, but they do not have a muscular layer. Veins carry blood back to the heart and have thinner walls with less smooth muscle. The aorta is a large artery with a substantial muscular and elastic wall but is not the smallest arterial branch. So the vessel described is the arteriole.