Functions of erythrocytes

• Erythrocytes are flat, disc-shaped cells, also known as biconcave discs.
• Red blood cells are responsible for oxygen transport, carbon dioxide transport, and the acid-base buffering.
• Hemoglobin carries oxygen, carbon dioxide and hydrogen.
• Erythrocytes contain a large quantity of carbonic anhydrase (CA).
• CA and hemoglobin together have roles in acid-base buffering.
• The shape and content of RBCs are ideally suited to carry out their primary function: transporting oxygen.
• The unique shape of erythrocytes, biconcave, contributes to the efficiency of oxygen transport by maximizing the ratio of surface area to volume.
• Erythrocytes contain no nucleus, organelles, or ribosomes.
• Red blood cells are mainly plasma membrane-enclosed sacs full of hemoglobin.
• The cell requires energy for cell metabolism and to preserve the membrane integrity.
• Erythrocytes must rely entirely on glycolysis for ATP formation due to the lack of mitochondria.
• Secondary polycythemia is an appropriate erythropoietin-induced adaptive mechanism, also known as physiologic polycythemia.
• Carbonic anhydrase catalyzes the reaction: H2O + CO2 ↔ H2CO3.
• The same enzyme can also catalyze the reverse reaction: H2CO3 ↔ H2O + CO2.
• The red cell count in secondary polycythemia commonly rises to 6 to 7 million/mm3.
• Whenever the tissues become hypoxic due to too little oxygen in the breathed air, such as at high altitudes, or due to failure of oxygen delivery to the tissues, such as in cardiac failure, the blood-forming organs automatically produce large quantities of extra red blood cells, a condition known as secondary polycythemia.
• The average number of red blood cells in men is 5,200,000 (± 300,000) / mm3.
• The average number of red blood cells in women is 4,700,000 (± 300,000) / mm3.
• People living at high altitudes have greater numbers of RBCs.
• Generating new red blood cells is a process known as erythropoiesis.
• In children, most bones are filled with red bone marrow that is capable of blood cell production until age 5.
• Blood oxygen content is determined by PO2, Hb level, and Hb function.
• Erythropoietin acts on bone marrow to stimulate red blood cell production.
• Blood flow, which is determined by Cardiac output, Peripheral perfusion, and Oxyhaemoglobin, is a crucial factor in oxygen delivery.
• The main sites of adult blood cell production include the vertebrae, pelvis, ribs, sternum, skull and upper ends of the long bones.
• Amino acids, lipids, and carbohydrates are also necessary for the production of RBCs.
• Renal tissue hypoxia and hypoxia-inducible factor-1 (HIF-1), an oxygen-sensitive transcriptional activator, are involved in the transcription of erythropoietin mRNA and renal erythropoietin synthesis.
• Laboratory-produced erythropoietin is often used to boost RBC production in patients with suppressed erythropoietic activity, such as those undergoing chemotherapy for cancer.
• The marrow of the long bones, except the proximal portions of the humerus and tibia, becomes quite fatty and produces no more RBCs after about age 20 years.
• Exposure to high altitude and Testosterone also stimulate the release of EPO.
• For the production of RBCs, Vit B12 and folic acid are needed for DNA synthesis, so they are necessary for the reproduction of all body cells, especially in hematopoietic tissue.
• Erythropoietin (EPO) is a glycoprotein secreted from kidneys (90%) and liver (10%).
• As a person matures, fatty yellow bone marrow replaces red marrow and it is incapable of erythropoiesis gradually.
• Erythropoietin stimulates the production of "Proerythroblasts" and speeds up the passage through different stages of erythropoiesis, increasing maturation rate.
• The principal stimulus for red blood cell production is "low oxygen" states.
• Reduced O2 delivery to the kidneys stimulates them to secrete the hormone erythropoietin (EPO) into the blood.
• Exposure of the blood to low oxygen for a long time results in growth induction, differentiation, and production of greatly increased numbers of RBCs.
• A Hb molecule has two parts: the globin portion, a protein made up of four highly folded polypeptide chains, and heme groups, four iron-containing non-protein groups.
• Each of the 4 iron atoms in hemoglobin can combine reversibly with one molecule of O2.
• Almost all of the iron delivered by transferrin to the bone marrow is incorporated into new red blood cells.