Which of the following is NOT one of the major parts of the circulatory system?

The pancreas is the structure that is not part of the circulatory system. The circulatory system is primarily comprised of the heart, veins, and capillaries, which work together to transport blood, nutrients, oxygen, carbon dioxide, and hormones throughout the body.

The heart is the muscular organ responsible for pumping blood. Veins carry deoxygenated blood back to the heart from the body, while capillaries facilitate the exchange of oxygen, nutrients, and waste products between blood and tissues. The pancreas, on the other hand, is an organ that plays a key role in the digestive system and in the regulation of blood sugar levels through insulin production, but it does not participate in the circulatory system's primary functions.