Anemia and red blood cells
Anemia is a condition in which red blood cell count is so low that not enough oxygen is carried to all parts of the body. Imagine that a person’s blood is a river. Traveling on this river are special barges (red blood cells) that carry parcels (oxygen), each barge carries only a specific amount of oxygen. If a person doesn't have enough of these barges, it's impossible to deliver enough oxygen, and as a result, they will start to feel weak and tired. A short climb up the stairs may leave someone breathless.
Remember, red blood cells are the barges that carry oxygen throughout the bloodstream to feed tissues. Hemoglobin, the primary component of red blood cells, is a complex molecule and is the oxygen carrier of the red blood cell. The body works very hard to ensure that it produces just enough red blood cells to successfully carry oxygen. Red blood cells live only 90 to 120 days. The liver and spleen get rid of the old cells, although the iron in the cells is recycled and sent back to the marrow to produce new cells.