Which of the following best describes arterioles?

Arterioles are small blood vessels that play a critical role in the circulatory system by connecting arteries to capillaries. This connection is essential because arterioles regulate blood flow from arteries into the capillary networks, where the exchange of nutrients, gases, and waste occurs. Their relatively small diameter allows them to control blood flow through vasoconstriction and vasodilation, thereby influencing blood pressure and distribution to various tissues. By contracting or relaxing, arterioles can increase or decrease blood flow to specific areas of the body as needed, making them vital for maintaining proper circulation and homeostasis.

The other options describe structures or functions not characteristic of arterioles. For example, stating that they are large blood vessels mischaracterizes their size and function. Gas exchange occurs primarily in the capillaries, not in arterioles. Additionally, it is the veins that are responsible for returning blood to the heart, rather than arterioles, reaffirming the unique role that arterioles play in the cardiovascular system.