Let's go!
We've been down to the big toe to pick up the carbon dioxide released from the cells and and now need to make our way back to the heart. The veins are the highways back to the heart, so we make our way up through the leg and the torso to the main highway, the inferior vena cava. "Inferior" means below, so this collects us blood from everywhere below the heart.
There is also the superior vena cava ("superior" means above) that collects everyone that went to places above the heart - the head, chest, and arms.
The vena cavae are the entry points into the right side of the heart. You're wondering why it's called the right side when clearly it's on the left side of the picture? You're looking at this heart from the front, so how it would look to you in the chest of someone sitting across the table.
