Blood.
well, yes mostly all veins carry deoxygenated blood, except for two. The pulmonary vein that carry blood from the lungs to the heart and the umbilical veins carry oxygenated blood. In general, veins are the vessels that carry blood into the heart. However, the pulmonary veins carry oxygen rich blood to the heart, and the pulmonary arteries carry oxygen poor blood to the lungs. So, in short: no they do not carry blood all the time; the pulmonary veins carry oxygenated blood. Source(s): B.S. in Biology. Therefore, most veins carry deoxygenated blood and most arteries carry oxygenated blood. However, the pulmonary veins carry oxygen rich blood to the heart, and the pulmonary arteries carry oxygen poor blood to the lungs. So, in short: no they do not carry blood all the time; the pulmonary veins carry oxygenated blood. Source(s): B.S. in Biology. Arteries carry blood (with oxygen) from your heart out to your body, while veins carry blood (without oxygen) from your body to your heart. Arteries are strong, flexible blood vessels that are able to expand (get bigger) and contract (get smaller). They expand as your heart beats, and contract between heartbeats. Arteries carry oxygenated blood away from the heart to the body, and veins carry oxygen-poor blood back from the body to the heart. Your body also contains other, smaller blood vessels. Here is how blood travels in vessels through the body: The pulmonary veins carry relatively oxygenated blood from the lungs to the heart. The superior and inferior venae cavae carry relatively deoxygenated blood from the upper and lower systemic circulations, respectively. The portal venous system is a series of veins or venules that directly connect two capillary beds. The arteries are perceived as carrying oxygenated blood to the tissues, while veins carry deoxygenated blood back to the heart. This is true of the systemic circulation, by far the larger of the two circuits of blood in the body, which transports oxygen from the heart to the tissues of the body. A SecondsCount.org answered. Most veins carry blood that is low in oxygen back to the heart. After the oxygen and nutrients have been delivered to the body’s tissues by the arteries and capillaries, a second network of venules and veins carries blood and waste products back to the heart.  Arteries carry oxygenated blood (with the exception of the pulmonary artery and umbilical artery). Veins carry deoxygenated blood (with the exception of pulmonary veins and umbilical vein). There are two types of blood vessels in the circulatory system of the body: arteries that carry oxygenated blood from the heart to various parts of the body and veins that carry blood towards the heart for purification. In the circulatory system, veins (from the Latin vena) are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart. In contrast to veins, arteries carry blood away from the heart. Veins are less muscular than arteries and are often closer to the skin. The arteries are perceived as carrying oxygenated blood to the tissues, while veins carry deoxygenated blood back to the heart. This is true of the systemic circulation, by far the larger of the two circuits of blood in the body, which transports oxygen from the heart to the tissues of the body. Report Abuse. All veins carry bad blood that needs oxygen to the heart, to get it purified. Exceptions are the veins that contain good (oxygenated) blood to the heart walls -- to make the heart pump good blood to the whole of the body through the arteries. Sounds confusing but that is a fact.  Submit. · just now. Report Abuse. No, all the veins carry deoxygenated blood and the arteries carry oxygen rich blood But there is and exception, it's called the Pulmonary vein It carries blood from the lungs to the left atrium of the heart Because of it's direction it's called 'vein' But it carries oxygenated blood. Source(s): 5th grade science. Arteries carry blood away from the heart, and into and lungs to get oxygen. Then it is sent out through the body, and veins carry blood back to the heart. Look near the bend of the arm. Right pulmonary veins. Veins are the blood vessels that carry blood to the heart. Pulmonary veins are responsible for carrying oxygenated blood from the lungs back to the left atrium of the heart. This differentiates the pulmonary veins from other veins in the body, which are used to carry deoxygenated blood from the rest of the body back to the heart. 
https://au.answers.yahoo.com/question/index?qid=20100319224228AAnstjR https://au.answers.yahoo.com/question/index?qid=20100319224228AAnstjR https://www.sharecare.com/health/circulatory-system-health/what-difference-between-an-artery-and-a-vein https://en.wikipedia.org/wiki/Vein https://www.sharecare.com/health/circulatory-system-health/how-veins-carry-oxygen-body http://www.diffen.com/difference/Arteries_vs_Veins https://en.wikipedia.org/wiki/Vein https://answers.yahoo.com/question/index?qid=20110715100623AARdjBI https://answers.yahoo.com/question/index?qid=20121112191718AA4qJw2 http://www.healthline.com/human-body-maps/right-pulmonary-veins
what do veins carry