Red blood cells flowing

Red blood cells, or erythrocytes, are the most abundant cells in human blood, responsible for transporting oxygen from the lungs to body tissues.

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Red blood cells, also known as erythrocytes, are specialized blood cells responsible for oxygen transport. Their biconcave shape and lack of a nucleus allow greater flexibility to pass through narrow capillaries and maximize surface area for gas exchange. Each red blood cell contains about 270 million hemoglobin molecules, a protein that binds oxygen in the lungs and releases it in tissues.

Red blood cell production occurs in the red bone marrow, particularly in bones such as the sternum, ribs, and vertebrae. The hormone erythropoietin, produced by the kidneys, stimulates this production in response to low oxygen levels. A healthy individual produces approximately 2 million red blood cells per second, maintaining a stable count of 4.5 to 5.5 million per microliter of blood.

The lifespan of a red blood cell is about 120 days. After that, they are removed from circulation by the spleen and liver, where their components are recycled. Iron from hemoglobin is reused to produce new cells, while the remainder is converted into bilirubin, excreted in bile. Disorders such as anemia (low count) and polycythemia (high count) can significantly affect health, causing fatigue or risks of thrombosis, respectively.

Frequently Asked Questions

What are red blood cells?

Red blood cells, or erythrocytes, are blood cells that transport oxygen from the lungs to tissues and help remove carbon dioxide.

Why do red blood cells lack a nucleus?

The absence of a nucleus allows more space for hemoglobin and greater flexibility to pass through narrow capillaries, while also reducing the cell's own oxygen consumption.

What happens when there is a low red blood cell count?

A low count, called anemia, reduces oxygen-carrying capacity, leading to fatigue, pallor, and shortness of breath.