Give a reason why the blood vessel has thickest and most elastic wall?

The aorta, the main artery that carries blood away from the heart, has the thickest and most elastic wall of any blood vessel in the body. This is because the aorta is subjected to the highest pressure of any blood vessel, as it receives the full force of the heart's contractions. The thick and elastic walls of the aorta help to dampen this pressure and prevent the artery from rupturing.