What is the primary function of red blood cells?

Red blood cells play a crucial role in the circulatory system, primarily serving the function of transporting oxygen from the lungs to the rest of the body. They contain a protein called hemoglobin, which binds to oxygen molecules. This specialized structure allows red blood cells to efficiently pick up oxygen in the lungs and deliver it to tissues and organs, where it is needed for cellular respiration and energy production.

In addition to oxygen transport, red blood cells also help to carry a small amount of carbon dioxide back to the lungs, where it can be exhaled. This function is vital for maintaining the body’s respiratory and metabolic processes.

The other options describe functions associated with different types of cells. For example, white blood cells are primarily responsible for fighting infections, while the endocrine system is responsible for hormone production. Waste removal is generally handled by the kidneys and other systems, not directly by red blood cells. Thus, the primary and most significant role of red blood cells remains the transport of oxygen.