McDonald's Airport Toys. While on the surface it sounds like a good idea: get an airplane as a toy and turn your Happy Meal box into the airport. However, when our clown-faced friend unveiled what has come to be known as the cheapest McDonald's toy of all time, kids were not excited.
Oxygen is carried in the blood in two forms: (1) dissolved in plasma and RBC water (about 2% of the total) and (2) reversibly bound to hemoglobin (about 98% of the total). At physiological PO2 (40 &#60; PO2 &#60; 100 mm Hg), only a small amount of oxygen is dissolved in plasma since oxygen has such a low solubility.
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. MayDay Â· 6 years ago.