Simplify the following text for a Grade 2 native English-speaking person.
Original: In the circulatory system , veins ( from the Latin vena ) are blood vessels that carry blood towards 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 .
Simplified: All veins carry blood to the heart .