Video 6 Red Blood Cell Function

06) Red cells

After plasma, red blood cells make up the next largest component of the blood stream, accounting for nearly all of the remaining 45% of blood volume. Red cells function to carry oxygen molecules to tissue cells throughout the body and carry away waste carbon dioxide from the tissue cells.

The workhorse of the red cell is a small protein molecule called hemoglobin, which attaches to oxygen molecules in the capillaries of the lungs. Iron molecules are a critical component of the hemoglobin surface receptors, which bind to the oxygen molecule. Once oxygen molecules are released, the hemoglobin receptors pick up carbon dioxide molecules, which is a waste by-product formed in the tissue cells.

Hitching a ride on the hemoglobin molecule the carbon dioxide molecules are carried through the veins back to the heart, which pumps them to the lungs where the red cells release the carbon dioxide and pick up fresh oxygen molecules. Then they travel back to the heart and are in turn pumped through the arteries to all the tissue cells of the body. Hemoglobin also plays an important role in helping red cells hold their normal shape and therefore their smooth flow through plasma. Red cells live for approximately four months. When they die they are broken down and their components are recycled in the spleen.