What type of blood do all veins, except the pulmonary artery, carry?

All veins, except for the pulmonary vein, carry deoxygenated blood. Venous blood is typically returning to the heart after circulating through the body, where it has delivered oxygen to tissues and collected carbon dioxide and other waste products. The primary role of veins is to transport this deoxygenated blood back to the heart, where it can then be sent to the lungs for re-oxygenation. The only exception to this is the pulmonary veins, which carry oxygenated blood from the lungs to the heart.

The terminology surrounding blood characteristics can be a source of confusion. While some might use terms like "impure blood" to describe deoxygenated blood, it is more accurate to say that deoxygenated blood is simply lacking in oxygen that is necessary for tissue nourishment and not truly "impure." Enriched blood is also not a commonly accepted term in the context of describing blood's oxygen content. Therefore, the best answer in this context is deoxygenated blood, as it accurately reflects the state of blood returning to the heart through the veins.