section_path: Structure/Blood vessels/Veins
section_name: Veins
paragraph_text: Veins
  
  Capillaries merge into venules, which merge into veins. The venous system feeds into the two major veins: the superior vena cava – which mainly drains tissues above the heart – and the inferior vena cava – which mainly drains tissues below the heart. These two large veins empty into the right atrium of the heart.