Ask your child to make a fist with her right hand. Explain that their fist is about the same size as their heart. So when they were a baby, their heart was smaller, and your heart is bigger than theirs.
Trace the child's right fist on a piece of white drawing paper with a pencil. Be sure to trace it in the center of the paper so you can add the valves, which bring blood into the heart and back out. The fist should look similar to a real heart, and it will help children visualize the organ.
Draw two circles side by side that will be the right and left atrium. The right atrium should be placed on the left side, while the left atrium is on the right because we are looking at a heart face on. They should take up the top half portion of the heart and roughly be the same size. Then draw two vertical oval shapes next to each other underneath the atriums. The right ventricle is underneath the right atrium, and the left ventricle is underneath the left atrium. These are the four chambers of the heart.
Draw the pulmonic valve coming out of the right ventricle and across the left atrium. Then it splits to the your right, to the pulmonary artery and the left lung. It also splits to your left and the pulmonary artery and right lung. Behind the right side of the heart, which will be drawn on the left, is the main vein that brings blood from the body and into the heart. Draw it like a finger-sized cylinder. The top part is the superior vena cava, and the lower portion is the inferior vena cava. Color them blue and color the right atrium, right ventricle and the pulmonary artery blue.
Draw the aorta like a finger-sized cylinder coming out from the bottom of the heart. Then draw a connecting aorta from the left ventricle going underneath the pulmonary artery and out the top separating into four arteries at the top. Color this red, and also color the left atrium and left ventricle red.
Describe to children than the blue side of the heart takes blood in from the body. It is blue because it needs oxygen. The heart contracts and pushes oxygen and blood into the red areas, and then the heart contracts again, pushing the blood with oxygen into the rest of the body.