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.
Veins are the blood vessels that carry blood back to the heart. They may contain valves which stop blood flowing away from the heart. The heart works by following a sequence of electrical signals that cause the muscles in each chamber to contract in a certain order. blood vessel's main function is to transport blood around the body. Blood vessels also play a role in controlling your blood pressure. Blood vessels are found throughout the body. There are five main types of blood vessels: arteries, arterioles, capillaries, venules and veins.