Biconcave disc characteristic red color and transport oxygen from the lungs to the tissues. Mature red blood cells are round and biconcave because they lack a nucleus and unlike other cells, red cells require a small amount of oxygen for its metabolism and most oxygen is freed into the tissues. The absence of nucleus, ribosomes, and mitochondria partly contributes to the red blood cell’s disc-like structure which leaves room for hundreds of millions of hemoglobin molecules found within the cells. Hemoglobin is a red and iron-rich protein that merges with oxygen to carry oxygen from the lungs to the body tissues. Both
Red blood cell second in human adults. The cells develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Each circulation takes about 60 seconds (one minute). Approximately a quarter of the cells in the human body are red blood cells. Nearly half of the blood's volume (40% to 45%) is red blood cells. Packed red blood cells (pRBC) are red blood cells that have been donated, processed, and stored in a blood bank for blood transfusion. Almost all vertebrates, including all mammals and humans, have red blood cells. Red blood cells