Question

Arteries and veins are joined by a network of—

Answer 1

Hint: Arteries carry oxygenated blood from heart to all the body organs. These vessels are thick and elastic. Veins carry deoxygenated blood from all the body parts to heart. These vessels are thin and elastic.

Complete answer:
 Heart pumps blood throughout the body. The circulatory system as a whole comprises of— arteries, veins and capillaries and the major organ heart. Both arteries and veins are joined with a huge interconnecting network of capillaries throughout the body.
Arteries are blood vessels that carry oxygenated blood. These carry the blood from the heart and transport it to various organs of the body. These vessels are thick and elastic in nature. These further form small multiple interconnecting networks to transport the blood to every cell in the body known as capillaries. The only exception in the case of arteries is the pulmonary arteries which carry deoxygenated blood.
Veins are the vessels in the body which carry deoxygenated blood. These collect the deoxygenated blood from all the organs and transport it back to the heart. These vessels are fragile, thin and elastic. These lie closer to the skin. The only exception in the case of veins is pulmonary veins and umbilical veins. These carry oxygenated blood.
Capillaries are vessels that connect arteries and veins. These promote exchange of elements between the blood and cells.

Note: Both veins and arteries form small interconnecting networks called capillaries. This causes exchange of elements between the bloodstream and the connecting tissue. The capillaries are very thin in nature.