What is the primary role of red blood cells in the blood?

The primary role of red blood cells, also known as erythrocytes, is to carry oxygen from the lungs to the body's tissues and organs. These cells contain hemoglobin, a protein that binds to oxygen molecules, allowing them to be effectively transported through the bloodstream. This function is critical because every cell in the body requires oxygen to perform cellular respiration, a process that generates energy necessary for survival.

While other roles in the body involve different blood cells—such as white blood cells, which are responsible for fighting infections, and plasma, which helps transport nutrients and waste—red blood cells specifically focus on oxygen transport. Therefore, their ability to pick up oxygen in the lungs and deliver it to tissues is vital for maintaining proper physiological function. This oxygen transportation is essential for keeping the body's systems running smoothly and ensuring overall health.