Why is the movement of oxygenated faster than that of de-oxygenerated blood?

Answer 1

Oxygenated blood is pumped from the (left side of the) heart through the arteries and so is under a relatively high degree of pressure from there which contributes to its "speed." Additionally, arteries have a good mix of muscular and elastic tissue which also help propel blood along. Deoxgenated blood travels back to the heart through veins. Veins have larger lumens and lack the degree of muscular and elastic tissue that arteries have. They are also are too far from the heart to benefit from the pumping action from it AND they have to work against gravity. As a result, veins depend on muscle contractions in your lower limbs to squeeze the blood upward towards the heart. As you might imagine this isn't nearly as fast as a heart that pumps blood forward 60 to 80 times a minute and so deoxygenated venous blood moves much slower that oxygenated arterial blood.