Erythrocytes (red blood cells): characteristics and function

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

We will see below what erythrocytes are, how they are produced and what their main functions are.

• Related article: "Major cell types of the human body"

What are erythrocytes?

Erythrocytes are the red cells that make up our blood. In fact, the term "erythrocyte" comes from the Greek "erythrós" which means red, and from "kytos" which means cell.

Also called red blood cells, erythrocytes are one of the main components of blood, whose functions are essential to maintain the different systems of our body. To analyze this in greater 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 38º C (one degree higher than body temperature). The amount in liters of blood that each of us have depends largely on our height and weight.

Its main functions include transporting oxygen from the lungs to the cells of the body, transport hormones, supply cells with specific nutrients, eliminate waste products Y keep the body in natural balance (for example, pH levels and temperature).

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

99% of this other half is made up of red cells that 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.

• You may be interested: "Blood phobia: everything you need to know about hematophobia"

Red blood cell functions

Erythrocytes are shaped like small, grooved discs. They are flexible, that is, they can be easily bent to circulate through the narrowest blood vessels.

Unlike other cells, erythrocytes do not have a nucleus. What they do have is hemoglobin, a protein responsible for transporting oxygen through the blood, and is also responsible for the red color of the blood. Among the main functions of red blood cells 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 cellular metabolism, generating in turn carbon dioxide as a waste.
• They collect carbon dioxide and carry it back to the lung, allowing us to expel it when exhaling.
• They release hydrogen and nitrogen, which helps keep the PH level of the blood stable.
• Through this, the blood vessels expand and blood pressure is lowered.

On the other hand, the 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 turn into blood cells or platelets.

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

Glucose is essential for their metabolism (since they do not have a nucleus or mitochondria), therefore, some of the main pathways are glycolysis and the hemoglobin reductase pathway.

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

Red blood cells have an approximate life cycle of 120 days. After this time they break down in the bone marrow, spleen or liver, through a process known as hemolysis. In this process, building blocks of red blood cells, such as iron and globin, which are later reused.

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). Etymologies of Chile. Retrieved October 17, 2018. Available in http://etimologias.dechile.net/?eritrocito.
• Erythrocytes (Red Blood Cells) (2014). National Cancer Institute. Retrieved October 17, 2018. Available in https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0022014/.
• What does blood do? (2015). U.S. National Library of Medicine. Retrieved October 17, 2018. Available in https://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072576/.