As the heart beats, it pumps blood through a system of blood vessels, called the circulatory system. Arteries carry oxygen-rich blood away from the heart to all of the body's tissues. These are small, thin blood vessels that connect the arteries and the veins.
The heart is shaped something like a cone, with a pointed bottom and a round top. It is hollow so that it can fill up with blood. An adult's heart is about the size of .
With the first breaths of air the baby takes at birth, the fetal circulation The baby's circulation and blood flow through the heart now function like an adult's.