Final answer:
Erythrocytes, or red blood cells, transport oxygen from the lungs to the body's tissues, supporting cellular respiration.
Step-by-step explanation:
Erythrocytes, also known as red blood cells (RBCs), have the main function of carrying oxygen in the blood. They contain a protein called hemoglobin, which binds with oxygen and transports it to the body's tissues.
Erythrocytes pick up inhaled oxygen from the lungs and deliver it to the cells, providing oxygen for cellular respiration. Therefore, the main function of erythrocytes is to transport oxygen to tissues.