*full answer in attachment*
As the blood in the human body flows from the heart to all the
cells of the body it passes through a branching system of blood vessels getting finer and finer until it reaches the capillaries, through which, chemicals diffuse to every cell of the body. This is shown schematically in the figure at the right. In the table below is shown the average diameter of the vessels at each level of branching – aorta, arteries, arterioles, and capillaries – and the average speed of blood that flows through them.
Vessel type Diameter (cm) Aorta
8×10-4 Average speed of flow
Blood vessels have circular cross section.
Area = πr2