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.
blood towards the heart and also have valves. The capillaries link arteries and veins, and have a one cell thick wall. Blood is made up of four main things plasma, the liquid part of the blood; Red Blood Cells to carry oxygen; White Blood cells to protect the body from disease and platelets to help blood clot. Blood used by the body is brought back to the heart and lungs by the veins of the body.