A B-double or consists of a prime mover towing two semi-trailers, where the first semi-trailer is connected to the prime mover by a fifth wheel coupling (aka 'converter dolly') and the second semi-trailer is connected to the first semi-trailer by a fifth wheel coupling.
1 Arteries. 2  Arteries are elastic vessels that transport blood away from the heart. 3  Pulmonary arteries carry blood from the heart to the lungs where oxygen is picked up by red blood cells. 4  Systemic arteries deliver blood to the rest of the body. 5  Veins. 6  Veins are elastic vessels that transport blood to the heart.
Arteries carry blood away from the heart, while veins carry blood towards the heart. Capillaries carry blood from arteries to veins. Arteries generally carry oxygenated blood from the heart to the tissues and organs during the systolic heartbeat cycle. They are under high pressure. (the only exception is the pulmonary arteries which carries deoxygenated blood from the heart to the lungs).