What is the function of red blood cells?

Red blood cells, or erythrocytes, primarily transport oxygen from the lungs to the body's tissues.

Red blood cells (RBCs), also known as erythrocytes, play a crucial role in the transportation of oxygen from the lungs to the body's tissues and the removal of carbon dioxide from the tissues to the lungs. This is made possible by a protein called haemoglobin, which is found in abundance in these cells. Haemoglobin has a high affinity for oxygen, allowing it to bind with oxygen molecules in the lungs and carry them to the body's tissues.

RBCs are unique in their structure, which is optimised for their function. They are biconcave discs, which increases their surface area to volume ratio, allowing for efficient gas exchange. This shape also provides flexibility, enabling them to navigate through the narrowest blood vessels.

Furthermore, RBCs lack a nucleus and other organelles, providing more space for haemoglobin and thus increasing their oxygen-carrying capacity. The absence of a nucleus also means that RBCs cannot repair themselves or reproduce, resulting in a lifespan of about 120 days.

In addition to oxygen transport, RBCs also play a role in the body's immune response. They have a negative surface charge which causes them to repel each other and prevents them from sticking to each other or the vessel walls. This property, known as zeta potential, helps to maintain smooth blood flow.

In summary, the primary function of red blood cells is to transport oxygen from the lungs to the body's tissues. Their unique structure and properties, such as the presence of haemoglobin, their biconcave shape, and their zeta potential, all contribute to their ability to perform this function efficiently.