Red blood cell (erythrocyte)

Structure and distinguishing features

Mammalian red blood cells are notable for their biconcave disc shape, which increases surface area for gas exchange and allows flexible passage through narrow capillaries. Mature human erythrocytes lack a nucleus and most organelles, maximizing space for the oxygen-binding protein hemoglobin. Hemoglobin contains iron and gives red blood cells their characteristic color.

Production, lifespan and removal

Erythrocytes are produced by erythropoiesis in bone marrow under hormonal regulation (e.g., erythropoietin). A healthy red blood cell circulates for about 100–120 days before being removed by the spleen and liver, where its components are recycled. Disruption in production or premature destruction alters blood counts and oxygen delivery.

Functions and clinical importance

Beyond oxygen delivery and carbon dioxide transport, red blood cells contribute to acid–base balance and blood viscosity. Clinically, deviations from normal counts or shape can indicate disease: anemia denotes low red cell mass or hemoglobin; polycythemia is an excess of cells; inherited disorders such as sickle cell disease change cell shape and function. Laboratory measures (RBC count, hemoglobin, hematocrit, mean corpuscular volume) help diagnose and monitor many conditions.

Notable facts and distinctions

• Non-mammalian vertebrates often retain nuclei in their red blood cells.
• Red blood cells have inspired medical diagnostics and treatments, including transfusion medicine and therapies targeting hemoglobin disorders.
• Alterations in red cell number or appearance are among the most common findings in routine blood tests.

For introductory summaries and further reading on physiology and disorders, see basic hematology resources and reviews. Additional technical details are available through specialized texts and clinical guidelines.