What does it mean by double circulation?

What is pulmonary circulation?

What is the advantage of these separate circulatory systems?

What is the role of arteries?

How does the structure of the arteries help it to withstand the high pressure exerted by the heart?

What is the role of the capillary?

How does the structure of capillaries relate to its function?

What are the functions of veins?

What is the inferior vena cava?

What is the superior vena cava?

The blood at low pressure has to be returned to heart, how is this achieved?