Final answer:
Red blood cells have structural characteristics that allow them to bind and deliver oxygen. They have no nucleus or organelles, allowing for more space to carry oxygen. Red blood cells have an average lifespan of 120 days and are recycled by phagocytic macrophages in the liver and spleen.
Step-by-step explanation:
Red blood cells (RBCs) have several structural characteristics that allow them to deliver oxygen to the cells of the body. They are flattened, disk-shaped cells with no nucleus and other organelles, which gives them more space to carry oxygen. Each RBC contains about 200 million molecules of hemoglobin, a protein that binds with oxygen. Hemoglobin also gives RBCs their red color.
Red blood cells have an average lifespan of 120 days. After this time, they are broken down and recycled by phagocytic macrophages in the liver and spleen. White blood cells, such as phagocytes, neutrophils, and lymphocytes, play a role in defending the body against foreign bacteria and pathogens.