According to Springfield Technical Community College, the primary role red blood cells play in the body is to transport oxygen from the lungs to the various body tissues. To carry out this task, the cells are filled with a substance called hemoglobin. Hemoglobin is so important to red blood cells that its molecules comprise one-third of the cell’s volume.
Springfield Technical Community College explains that red blood cells are so packed with hemoglobin that they lack nuclei. Because they lack nuclei and routinely become damaged by trying to squeeze through the tiny capillaries, red blood cells have a finite lifetime. Most red blood cells survive for about 120 days before they are replaced. During their lifetime, each red blood cell is thought to travel through the body about 75,000 times. Because there is no nucleus in each red blood cell, the cells carry the instructions for building hemoglobin in the free cytoplasm.
Damaged or improperly formed red blood cells can cause a condition called anemia, as explained by Springfield Technical Community College. One way this occurs is if the cells are deficient in hemoglobin. When the oxygen levels in the blood drop, the body reacts by producing more red blood cells.