Which type of blood vessel is characterized by three layers of tissue and carries oxygenated blood away from the heart?

The correct answer is characterized by having three distinct layers—an outer layer made up of connective tissue, a middle layer composed of smooth muscle and elastic fibers, and an inner layer called the endothelium. This structure allows for the regulation of blood flow and blood pressure. Arteries are designed to carry oxygenated blood away from the heart to the various tissues in the body, with the notable exception of the pulmonary arteries. The thick muscular walls enable arteries to withstand the high pressure of blood being pumped directly from the heart.

In contrast, veins and venules have thinner walls and are more compliant since they carry deoxygenated blood back to the heart, typically at lower pressures. Capillaries, on the other hand, are the smallest blood vessels and have walls consisting of a single layer of endothelial cells, facilitating the exchange of gases and nutrients at the tissue level. The structural differences among these vessels reflect their distinct roles in the circulatory system.