Jayden the Red Blood Cell has just entered the bloodstream for the first time and is excited to complete his first circulatory circuit! His friend Antoine also has matured and exited the bone marrow as well. 

Jayden needs to get to the lungs to get oxygenated blood to help fuel the body. He travels through the pulmonary artery to get to the lungs. Along the way, he and Antoine see many other red blood cells traveling through the bloodstream carrying carbon dioxide for the lungs to exhale. 

After a few seconds of traveling through the bloodstream, Jayden and Antoine have made it to the lungs. They are amazed at how big the lungs are and how strong they are pumping. Jayden then travels to the the pick-up for oxygen and he takes as much as he can carry. He and Antoine exit the lungs through the pulmonary vein, now headed to the heart. 

Jayden and Antoine have gotten their oxygenated blood and are traveling with the rest of the blood cells through the pulmonary vein. They are traveling to the heart now, more specifically the left atrium.

After traveling a few seconds in the pulmonary vein, Jayden and Antoine have made it to the Left Atrium. This is where Jayden and Antoine will rest until they need to go somewhere in the body. When they get signaled to go somewhere, the left atrium will pump them out extremely hard. 

Jayden has finally received his call to a part of the body that needs oxygen; the right calf muscle!  Sadly, Antoine has called elsewhere. Saying their goodbyes, they begin to head towards where they will be pumped out of the heart and into the Aorta from the Left Ventricle. 

After being pumped out of the left ventricle, Jayden finds himself traveling through the Aorta to the right calf muscle. Being the most powerful artery in the body, the Aorta takes a majority of the oxygenated blood to wherever it is going in the body.