Arteries taking oxygen rich blood from the heart connects to arterioles which have a smaller diameter compared to arteries.
Arterioles play a part in the regulation of arterial blood pressure, they branch out, connecting to capillaries.
Capillaries are extremely small, only one cell thick and have very thin walls, allowing the transfer of oxygen and nutrients contained in blood to tissues in the body, collecting carbon dioxide waste material which connecting to venules. Capillaries work as groups, not individually.
Venules which like capillaries are extremely small, they take the carbon dioxide and waste material connecting with veins.
Veins take the carbon dioxide and waste material back to the heart and ultimately into the lungs where it leaves the lungs through the normal act of breathing.
The Arterial system that supplies blood to every part of your body is quite amazing, excluding arteries, arterioles, venules and veins, there are around 9 billion capillaries in the adult human body, each capillary is around 5 micrometres thick. To give an idea how small that is, in metric there are 10,000 micrometres in 1 centimetre, in imperial, there are 25,400 micrometres in 1 inch. Another comparison is the human hair, one single strand of hair can measure around 100 micrometres wide. That means the width of one strand of hair, is the same width as 20 capillaries!