My name is Ruby; I am a red blood cell. I am a dazzling ruby red color (hence my name) with a small area of inner pallor and I am very small: only about 6 µm in diameter. I get my red color from a protein chemical called hemoglobin, which is bright red. Hemoglobin not only gives me my beautiful color, it also contains the element iron, which makes it a good vehicle for transporting oxygen and carbon dioxide. I have a very important role in the circulatory system of your body. Actually, it is probably the most important of all the blood cells. I carry oxygen to all parts of your body and tissues and I also return carbon dioxide from your tissues to your lungs.
So I bet you are wondering how I do this very important role! I enter the blood vessels through the heart’s main artery called the aorta making sure that I am full of oxygen. The forceful contraction of your heart’s left ventricle forces me into your aorta which then branches into many smaller arteries, which run throughout your body. The inside layer of your artery is very smooth, allowing me to flow quickly. The outside layer of your artery is very strong, allowing me to flow forcefully. I enter the capillaries full of oxygen, where the oxygen and nutrients are released. The waste products are collected and the waste-rich blood flows into your veins in order to circulate back to your heart and then allow the exchange of gases in your lungs. I eventually pass through your kidneys, which filter much of the waste from the blood.
I also pass through your small intestine. From the small intestine I meet with many of my family and friends that are also blood and we all collect in the portal vein that passes through your liver. Your liver filters sugars from me and stores them for later. As I pass through your lungs, oxygen molecules attach to the hemoglobin and when I pass through your body tissue, the hemoglobin releases the oxygen to the cells. Then the empty hemoglobin molecules bond with the tissue’s carbon dioxide or other waste gases, transporting it away.
After being in your lungs I have fresh oxygen and lots of it! I then enter your pulmonary veins and then return to your heart, re-entering through your left atrium. Then I pass through a one-way valve into your left ventricle where I will exit your heart through your main artery, called the aorta. Your left ventricle’s contraction forces the blood into the aorta and the blood begins its journey throughout the body once again and starts the entire process over again.
I eventually pass through your kidneys, which filter much of the waste from the blood. I also pass through your small intestine. From the small intestine I meet with many of my family and friends that are also blood and we all collect in the portal vein that passes through your liver. Your liver filters sugars from me and stores them for later.
Over time, I get worn out and eventually die. The average life cycle of a red blood cell like me is 120 – 130 days. Your bones are continually producing new blood cells from the red marrow of them, replenishing your supply. So don’t worry you will always have a red blood cell like me! There are actually over 30 billion red blood cells in your body as we speak! Two million disintegrate every second but don’t you worry because two million are also being created every second to replace the seniors.