A red blood cell can start in the big left toe of a person and travel all around the body, ending up in the same place it started. During the entire transportation process, the Red Blood Cells transport oxygen from the lungs to the body tissues and carbon dioxode from the body tissues to the lungs. Red blood cells can be found in every part of the body because they are so widely spread out.

Starting at the big left toe of a person, a deoxygenated red blood cell moves through many blood vessels starting with the veinules. Veinules are microscopic blood vessels that connect the smallest veins to capillaries, the smallest arteries. After moving through veinules, the deoxygenated Red Blood Cells move into the Saphenous Vein. Following this long trip up the leg, the blood travels to the Renal Veins where the blood is carried to and from the Kidney's. Blood also travels into the Hepatic Veins. The Hepatic Veins are part of the systemic circulation of the blood that transports deoxygenated blood from the digestive tract, to the Liver. The deoxygenated blood from the lower body and abdomen then flows into the Inferior Vena Cava. The Inferior Vena Cava is a large vein that collects blood from the lower half of the body and returns it to the Right Atrium of the heart. The Superior Vena Cava is the large vein that returns blood from the head, arms, and chest into the Right Atrium.

From the Right Atrium, the blood circulation through the heart begins. The blood is pumped though the Tricuspid Valve into the Right Ventricle where deoxygenated blood is pumped through the Pulmonary Semilunar Valve into the Pulmonary Artery. The deoxygenated blood is then carried to the left and right Lungs. In the Lungs, the red blood cells release their carbon dioxide and take up oxygen. Now the blood is oxygenated. Oxygenated blood enters Pulmonary Capillaries which combine into large Pulmonary Vein (the only veins which carry oxygenated blood) the oxygenated blood travels from the Pulmonary Vein into the Left Atrium, through the Mitral Valve and down to the Left Ventricle.

When the blood is pumped from the Left Ventricle, it encounters the Aortic Valve. The Aortic Valve regulates the blood flow from the Left Ventricle into the largest artery: the Aorta. The Aorta is the artery that carries blood to all parts of the body. The Aorta branches and forms arteries to transport oxygenated blood to all parts of the body. The arteries keep on branching off forming smaller and smaller vessels, concluding by forming capillaries. Every cell is near a capillary. The purpose of the Capillary is to regulate the exchange of materials between the blood and body tissues through the capillary walls. The cells take the oxygen across the capillary walls from the red blood cell and give up their carbon dioxode, making deoxygenated red blood cells.

In order for the blood to get back to the left big toe, it retraces the steps that it already took. It goes up the Aorta and back down the Abdominal Aorta. From the Abdominal Aorta it goes into the Mesenteric Artery. Then it goes down the Iliac Artery and into the very long Femoral Artery and down to the left toe.

A Red Blood Cell does start in one place and eventually ends up in the same place it started.