Awesome Anatomy

The most common type of blood cell is the red blood cell. These cells are used by all vertebrates as the primary method of delivering oxygen from either lungs or gills to the rest of the body. They are commonly called erythrocytes or RBCs to set them apart from other blood cells like leukocytes (white blood cells).



Most of a red blood cell is hemoglobin, a complex iron-based molecule. Heme groups in hemoglobin contain the iron, which links to oxygen to transport it throughout the body; they also carry some of waste carbon dioxide back to the lungs. About 2% of all oxygen and almost all carbon dioxide are dissolved in blood plasma, and myoglobin in muscle cells (related to hemoglobin) stores oxygen there as well. Hemoglobin’s iron is the reason erythrocytes are red. When depleted of oxygen, the hemoglobin takes on a bluish hue.


Red blood cells in mammals do not have a cell nucleus, and therefore do not have DNA; they also do not have other organelles like mitochondria, and produce energy through glycolysis of glucose – a fermentation process – followed by lactic acid production. Their glucose uptake is not regulated by insulin. They are shaped like disks with indentations on top and bottom, optimizing them for exchanging oxygen by maximizing surface area. They are also flexible, allowing them to fit into the tinest capillaries. Adult humans have 2-3 x 1013 red blood cells at any given time, with men and people living in high altitudes having more. Blood types are differentiated by different surface glycoproteins.