Which of the following is true about arteries?

• A. They carry blood toward the heart
• B. They carry blood away from the heart
• C. They exchange most of the gases with tissues
• D. They are the primary site of nutrient exchange

Answer: (B)

Arteries carry blood away from the heart. That directional role is what defines them in the circulation. In the systemic circuit, arterial blood is usually oxygen-rich as it travels from the heart to tissues, while the pulmonary arteries are an exception because they carry oxygen-poor blood away from the heart to the lungs for gas exchange. Arteries have thick, elastic walls to handle the high pressure of pumped blood and to help regulate blood flow through constriction and dilation.

Gas exchange with tissues happens mainly in the capillaries, which have tiny, thin walls that allow diffusion of oxygen, carbon dioxide, and nutrients. The site where nutrients and wastes are exchanged is also primarily the capillary network. Veins, not arteries, return blood toward the heart and often have valves to prevent backflow, with thinner walls than arteries.