What is the primary function of erythrocytes in the human body?

Erythrocytes, also known as red blood cells, have the primary function of carrying oxygen from the lungs to the tissues throughout the body. They achieve this through the protein hemoglobin, which binds to oxygen molecules. This crucial role ensures that all cells receive the oxygen necessary for cellular respiration, a process that produces energy. Additionally, erythrocytes help in transporting a portion of carbon dioxide, a waste product of metabolism, back to the lungs for exhalation. Their ability to efficiently transport gases is vital for sustaining life, providing the necessary energy for bodily functions. Other options, such as fighting infections, regulating body temperature, or transporting nutrients, are functions carried out by different components of the blood or other systems in the body.