What is the primary function of erythrocytes?

Erythrocytes, or red blood cells, have the primary function of transporting oxygen from the lungs to the tissues throughout the body. They achieve this through the protein hemoglobin, which binds oxygen molecules in the lungs and releases them as the red blood cells circulate through the bloodstream. This crucial transport of oxygen is essential for cellular respiration and energy production in the body's tissues.

While different types of blood cells and components serve other functions—such as leukocytes, which are involved in defending the body against infections, or platelets, which are key in blood clotting—erythrocytes are specifically designed for oxygen transport. Additionally, regulating blood pressure involves various factors such as blood volume and vessel constriction but is not a function performed by erythrocytes.