What is the primary function of red blood cells?

The primary function of red blood cells is to carry oxygen to tissues throughout the body. Red blood cells contain a protein called hemoglobin, which has a high affinity for oxygen. This allows them to efficiently pick up oxygen from the lungs and transport it through the bloodstream to various tissues and organs that require it for cellular respiration and energy production. The ability to transport oxygen is crucial for sustaining life, as it enables the body's cells to carry out their functions effectively.

While other elements of the circulatory system contribute to various functions—such as white blood cells fighting infections, platelets aiding in blood clotting, and plasma serving as a medium for transporting hormones and nutrients—none of these roles compare to the essential function of red blood cells in oxygen transport. This key role is why red blood cells are vital to overall health and bodily function.