Erythrocyte (Red Blood Cell): Structure, Function, and Clinical Importance

The erythrocyte (red blood cell, RBC) is the most abundant blood cell and the primary vehicle for oxygen transport.

Key Features

• Biconcave disc shape (≈7–8 µm diameter) – maximizes surface‑area‑to‑volume for gas exchange.
• No nucleus or organelles in mature cells – more space for hemoglobin.
• Contains ~270 million hemoglobin molecules per cell.

Function

Hemoglobin binds O₂ in pulmonary capillaries (high pO₂) and releases it in tissues (low pO₂). Also transports CO₂ (as carbaminohemoglobin and via bicarbonate).

Clinical Relevance

• Anemia – Low RBC count/hemoglobin → tissue hypoxia.
• Polycythemia – Excess RBCs → hyperviscosity, thrombosis risk.
• Hemolysis – Premature destruction → jaundice, anemia.

RBC indices (MCV, MCH, MCHC) and morphology on peripheral smear guide diagnosis.