There are three types of blood vessels (tubes) which carry blood around our body; arteries, veins and capillaries.
Arteries carry blood away from the heart. As the arteries get further away from the heart, they get smaller and branch into smaller vessles known as arterioles, which then split into tiny capillaries. The capillaries are tiny blood vessels which are found in all the body tissues. The capillaries give oxygen to the tissues and collect carbon dioxide, which is taken back to heart and then pumped to the lungs where it is excreted.
The capillaries are connected to the smallest veins in the body. The veins get bigger as they carry the blood back towards the heart.