Red blood cells flowing

Red blood cells, or erythrocytes, are blood cells that carry oxygen from the lungs to every tissue in the human body.

About this subject

Red blood cells are the most abundant cells in human blood, with about 5 million per microliter. Their biconcave shape increases surface area for gas exchange and allows them to deform as they pass through narrow capillaries. Hemoglobin, an iron-containing protein, gives them their red color and enables reversible oxygen binding. Produced in the red bone marrow, erythrocytes have an average lifespan of 120 days and are then removed by the spleen and liver. Their production is regulated by erythropoietin (EPO), a hormone released by the kidneys in response to low oxygen levels. Conditions such as anemia (reduced count or function) and polycythemia (excess) affect oxygen transport and can cause symptoms like fatigue and dizziness. The discovery of blood circulation by William Harvey in the 17th century and the identification of red blood cells by Antonie van Leeuwenhoek around the same time marked the beginning of modern hematology. In travel contexts, exposure to high altitudes can stimulate red blood cell production as an adaptation, a phenomenon exploited by athletes in training.

Frequently Asked Questions

What are red blood cells and what is their main function?

Red blood cells (erythrocytes) are blood cells that carry oxygen from the lungs to the tissues and help remove carbon dioxide. They contain hemoglobin, a protein that binds oxygen.

How long does a red blood cell live and where is it produced?

It lives about 120 days. It is produced in the red bone marrow from stem cells in a process called erythropoiesis.

What causes anemia and what are the symptoms?

Anemia can be caused by iron deficiency, vitamin B12 deficiency, blood loss, or chronic diseases. Symptoms include fatigue, paleness, shortness of breath, and dizziness.