Red blood cell

A red blood cell is a blood cell that transports oxygen. The red blood cell is also called the erythrocyte (erythros = red).

Structure of a red blood cell

A red blood cell is a biconcave disc-shaped cell with no nucleus, mitochondriae or ribosomes, and contains a large amount of haemoglobin, giving it its colour. Red blood cells bind oxygen in tissues because of the iron contained in their haemoglobin, their red pigment. There are 5 million erythrocytes per microlitre (one thousandth of a millilitre) of blood.

Like all blood cells they are produced in the bone marrow by maturation of haemopoietic stem cells. We refer to erythropoiesis, a permanent mechanism, which takes place to renew the store of red blood cells at a rate of 1% per day.

Function of the red blood cell

Erythrocytes carry oxygen molecules (O₂) from the lungs to all of the cells in the body and some of the carbon dioxide (CO₂) from the cells to the lungs. Glucose is the only source of energy for erythrocytes.

Red blood cells are responsible for the blood groups (ABO and rhesus systems) as they carry antigens on their cell surfaces.