What is the main function of erythrocytes?

Erythrocytes, commonly known as red blood cells, primarily function to transport oxygen from the lungs to the tissues throughout the body. This process is facilitated by hemoglobin, a protein within the erythrocytes that binds oxygen molecules efficiently. The oxygen is then released into the tissues where it is utilized for cellular respiration, critical for energy production.

Additionally, while erythrocytes do play a role in the transport of carbon dioxide back to the lungs for exhalation, their main and most vital function is the delivery of oxygen. Other options like the transport of nutrients or defense against pathogens are functions carried out by other cells or components of the blood, such as plasma and white blood cells, respectively. Thus, the role of erythrocytes is specifically centered on ensuring that oxygen reaches every part of the body, highlighting their essential function in maintaining aerobic metabolism and overall physiological homeostasis.