Why is the resistance to blood flow in the aorta greater than the resistance to blood flow in the vena cava?

Question

And Because the resistances is different, why can blood flow be the same?

Answer 1

Blood from the aorta is flowing into smaller and smaller vessels (arteries - arterioles - capillary network) which provides Peripheral Vascular Resistance.

Venous blood flows from the capillaries to the venules to the veins and into larger and larger capacitance vessels. The resistance for this is much lower. The capacitance vessels have very elastic and distensible walls compared to the arteries.

The blood flow is roughly the same because the heart can only pump out of the heart what has gone into the heart. There can be slight changes due to the distension of veins and pooling of blood in the venous circulation. This causes smaller volumes of blood to be pumped from the heart and causes the heart rate to speed up.