What is the primary function of erythrocytes (RBCs)?

The primary function of erythrocytes, or red blood cells (RBCs), is to carry oxygen to the tissues throughout the body. This vital role is accomplished through the use of hemoglobin, a protein within red blood cells that binds oxygen in the lungs and releases it in the tissues where it is needed for cellular metabolism. The efficient transport of oxygen is essential for sustaining life, as oxygen is crucial for the production of energy in cells.

While other functions related to blood and the circulatory system are important, such as fighting infections (which is primarily the role of white blood cells), regulating pH balance (which involves various components of blood including buffers), and transporting carbon dioxide (a different gas exchanged during respiration), these do not define the primary function of erythrocytes. The unique structure and composition of RBCs specifically enable their primary role in oxygen transportation.