Red blood cells, also called erythrocytes or red blood cells, are the cells that are found in greater proportion within the bloodstream. They are the fundamental anatomical units for all our vital functions. Among other things they transport oxygen and distribute nutrients throughout the body .

We will now look at what red blood cells are, how they are produced and what their main functions are.

What are red blood cells?

Red blood cells are the red cells that make up our blood. In fact, the term “erythrocyte” comes from the Greek “erythros” meaning red, and “kytos” meaning cell.

Also called red blood cells, erythrocytes are one of the main components of blood , whose functions are indispensable for maintaining the various systems of our body. To analyze this in more detail we will first see what blood is and what its functions and components are.

Blood and its main components

Blood is the fluid that runs through our body, whose composition is thicker than water, slightly viscous, and its average temperature is 38 º C (one degree higher than body temperature). The amount in liters of blood that each of us has depends largely on our size and weight.

Its main functions include transporting oxygen from the lungs to the cells of the body, transporting hormones, providing the cells with specific nutrients, removing waste products and keeping the body in natural balance (e.g. pH levels and temperature).

On the other hand, there are many cells that make up this liquid. 55% of the blood is plasma, a slightly yellow liquid composed of 90% water and 10% protein, electrolytes, vitamins, glucose, amino acids and other nutrients. The other 45% of our blood is made up of different types of cells.

Ninety-nine percent of this other half is made up of the red cells we call red blood cells or erythrocytes. The rest (1%) are white cells, also called leukocytes; and platelets , also known as thrombocytes. Thus, 84% of all cells in the human body are erythrocytes.

Functions of red blood cells

Red blood cells are in the form of small, indented discs. They are flexible, which means that they can bend easily to pass through the narrowest of blood vessels.

Unlike other cells, red blood cells have no nucleus. What they do have is hemoglobin , a protein in charge of transporting oxygen through the blood, and is also responsible for the red color of the blood. Among the main functions of erythrocytes are the following:

  • Collect oxygen from the air we inhale, and carry it through the blood vessels of the lung to all parts of the body.
  • This is the process necessary for cell metabolism, generating carbon dioxide as a residue.
  • They collect the carbon dioxide and take it back to the lung , allowing us to expel it when we exhale.
  • They release hydrogen and nitrogen, which helps keep the pH level of the blood stable.
  • Through this, the blood vessels expand and blood pressure decreases.

On the other hand, a deficit in the production of erythrocytes, or their accelerated destruction, is what causes anemia ; while an excess in the production of these cells generates polycythemia or erythrocytes.

Blood cell production process

Stem cells are responsible for generating the most solid parts of the blood. From a multi-stage development, stem cells become blood cells or platelets.

At the end of their development they are released into the bloodstream, which maintains a quantity of precursor cells that allows their regeneration . This last process is regulated by substances: the hormone erythropoietin (produced in the kidneys) is in charge of the production of red blood cells, and cytokines help the production of white blood cells.

Glucose is indispensable for their metabolism (as they have no nucleus or mitochondria), so some of the main pathways are glycolysis and the hemoglobin reductase pathway.

In adults, most blood cells are produced in the bone marrow , although in the case of red blood cells, specifically lymphocytes, maturation occurs in the lymph nodes.

Red blood cells have a life cycle of approximately 120 days. After this time they are broken down in the bone marrow, spleen, or liver, through a process known as hemolysis. This process preserves fundamental elements of the erythrocytes, such as iron and globin, which are then used again .

Bibliographic references:

  • Capellera-Garcia, S. and Flygare, J. (2016). Defining the minimal factors required for erythropoiesis through direct lineage conversion. Cell Rep., 14-15(11): 2550-2560.
  • Erythrocyte Etymology (2018). Etymology of Chile. Recovered October 17, 2018. Available at
  • Erythrocytes (Red Blood Cells) (2014). National Cancer Institute. Recovered October 17, 2018. Available at
  • What does blood do? (2015). U.S. National Library of Medicine. Retrieved October 17, 2018. Available at