Which structure in the body helps in transporting blood cells?

The structure responsible for transporting blood cells in the body includes all types of blood vessels: arteries, veins, and capillaries, making the choice of all of the above correct.

Arteries are essential for carrying oxygenated blood away from the heart to various tissues and organs. They are equipped to handle the high pressure exerted by the heart's contractions, and their muscular walls aid in maintaining blood flow.

Veins, on the other hand, are responsible for transporting deoxygenated blood back to the heart. They have thinner walls than arteries and often have valves that prevent the backflow of blood, ensuring it moves in the correct direction.

Capillaries play a crucial role at the microcirculation level. These small blood vessels are where the exchange of oxygen, carbon dioxide, nutrients, and waste products occurs between blood and surrounding tissues. Their thin walls facilitate this exchange effectively.

Thus, all these vessels — arteries, veins, and capillaries — work together to ensure that blood cells are transported throughout the body, making this answer comprehensive and accurate.