The coronary system is comprised of arteries, arterioles, capillaries, venules and veins. From the innumerable cardiac capillaries, blood flows back to the cardiac chambers through venules, which in turn coalesce into the cardiac veins. Most cardiac veins collect and return blood to the right atrium through the coronary sinus; there may or not be a Thebesian valve covering the ostium of the coronary sinus. The major venous vessels of the human heart are: coronary sinus, the anterior interventricular veins, left marginal veins, posterior veins of the left ventricle, and the posterior interventricular veins (see also the Coronary System Tutorial).
Yes, veins carry alot of carbon dioxide.
The function of the coronary artery is to carry oxygen and nutrients to the myocardium (heart muscle), it does not actually take the carbon dioxide away, (that is the job of the great and small cardiac veins).
oxygen
Carbon dioxide
The pulmonary veins are high in oxygen and low in carbon dioxide. All other veins are high in carbon dioxide and low in oxygen.
Plants give us oxygen we give them carbon dioxide.
carbon dioxide
carbon dioxide
Veins
The coronary veins drain into the coronary sinus, which in turn drains into the right atrium.
veins
coronary arteries and coronary veins