could you paraphrase this: An artery and vein are both types of blood vessels that are used to transport blood. The main function of an artery is that it enables oxygenated red blood cells to travel away from the heart to circulate throughout the body enabling all body parts to function. This is in contrast to veins which enable de-oxygenated blood to flow towards the heart. Both blood vessels have muscular walls but arteries are thick and elastic in structure due to the high pressure needed to push blood to all body parts when the left ventricle contracts, whereas veins have small muscular walls as they exhibit low pressure, e.g. enabling oxygenated red blood cells to travel from the lungs to the heart via the pulmonary vein. Additionally, veins contain valves to ensure blood flows only in one direction due to the valves opening and closing, whereas arteries don’t require valves because of the high pressure within the muscular walls enabling blood to flow in one particular direction.