What exactly is the function of our red blood cells?

Red blood cells (RBCs) also known as erythrocytes are the most abundant cell in the human body. With a staggering number of 25 trillion cells, yes TRILLION, the red blood cells make up around 80% of all your cells. The reason why we have so many of them is because they have a few incredibly important functions critical to our life.

Notice the characteristic donut-shape.

The red blood cells primary function is to carry oxygen from the lungs to all cells in our body. When we take a breath air rushes into the alveoli of our lungs. Here the oxygen in the air gets so close to the blood that the red blood cells are able to pick up some of the oxygen as they circulate through the lungs. With every heartbeat the cells get pumped through our circulatory system, and when a red blood cell reaches the thinnest type of blood vessels called capillaries, they are able to deliver their precious oxygen cargo to the nearby cells.

A single layer of cells (like the image above) will look yellowish/orange, the characteristic 

red color only appears when there are a lot of cells in one spot.

The oxygen is used by the cells in our tissues to make energy, and in that process carbon dioxide (CO2) gets produced as a waste product. Too much carbon dioxide can lead to a decreased pH in our blood (acidosis) which is not something we want. So the red blood cells pick up the CO2 and transport it back to the lungs where you are able to exhale it. Each cell makes this trip around the body around 200.000 times during its lifespan of 120 days before it gets retired by the spleen.

Their flat shape makes them able to fold and squeeze through narrow blood vessels called capillaries.

When our red blood cells only live for about 4 months, we constantly need to make more of them. So each second your body produces an impressive 2.4 million new ones to replace the ones we lose. But when each cell only measures 8 microns in diameter, we need a lot of them to fill our blood stream!

A short narrated video about the red blood cells and their function.