The term 'major blood vessel' refers to two large vessels that carry blood throughout the body. The first is an ARTERY, which is a six-letter word. Arteries are responsible for carrying oxygenated blood away from the heart and to the rest of the body. The second is an AORTA, which is a five-letter word. The AORTA is the largest ARTERY in the body and is responsible for carrying oxygenated blood from the heart to the rest of the body.