What are the differences between veins, arteries and capillaries?
Artery walls are thicker than veins and they carry blood away from the heart. Veins carry blood towards the heart, they are thinner walled than arteries and they have valves that you won’t find in arteries. Capillary walls are only one cell layer thick, this is the only blood vessel that allows for exchange of gases and nutrient and wastes. Arteries carry oxygen rich blood, the exception is the pulmonary artery. Veins carry oxygen poor blood, the exception being the pulmonary veins. That should give you a good start.
