Blood cell formation in bone marrow is called _ hemopoiesis __ hemopoiesis. Blood cell formation in lymphatic organs is called lymphoid hemopoiesis . Blood cells are produced from pluripotent __ stem __ cells (PPSC) which are also called hemocytoblasts . Erythrocytes are also called __ hemoglobin __ and RBCs. RBCs have two main functions. 1. RBCs pick up oxygen from the lungs and transport it to all the tissues of the body. 2. RBCs pick up CO2 from the tissues and transport it to the lungs where it is removed from the body. . It is the deficiency of life-giving _ hormonal control of erythopoiesis _ carried by RBCs that leads to death in cases of major trauma or hemorrhage. 4/2/2019 Page3
BIO 202IN: Human Anatomy and Physiology II RBCs are bi-concave discs that are about 7.5 micrometers in diameter. RBCs lose most of their organelles (including their nucleus) during development. Lacking mitochondria, RBCs are the only cells in the body that generate _ ATP _ anaerobically indefinitely. Lacking a nucleus and DNA, RBCs are incapable of _ protein _ synthesis and mitosis. The proteins spectrin and actin in the RBC membrane allow the cells to change shape to squeeze through capillaries. A large proportion of the cytoplasm is comprised of hemoglobin . Hemoglobin consists of 4 _ polypeptide _ chains called globulins. Each chain is connected to a non-protein heme group . Each heme group contains an iron atom (Fe 2+ ) which can bind to one O 2 molecule. Therefore each hemoglobin molecule can carry _ 4 _ 0 2 molecules. The hematocrit is the percentage of whole blood volume composed of _ red blood cells _. Normal hematocrit in males is 42% - 52% Normal hematocrit values in females is 37% - 48% RBC count and _ CO2 concentration are important clinical data because they determine the amount of O2 the blood can carry. The normal RBC count in males is 4.6 – 6.2 million per mm 3 The normal RBC count in females is 4.2 – 5.4 million per mm 3 The hemoglobin concentration , hematocrit , and RBC values tend to be lower in females than males. There are 3 reasons why these levels are lower in females. 1. Androgen levels are higher in males and stimulate _ testosterone _ production. 2. Monthly menses decreases RBC numbers. 3. Hematocrit is inversely proportional to percent body _47% +/- 5%males and 42% +/- 5% females___. 2.5 million RBCs are born every second. 2.5 million RBCs die every second. Red blood cell production is called erythropoiesis and it takes 3-5 days. Erythropoietin stimulates an erythrocyte colony-forming unit .to transform into an erythroblast. Erythroblasts multiply and synthesize _ hemoglobin __. The erythroblast’s nucleus shrivels and is displaced from the cell. The erythroblast has now become a _ mRNA __ named for the appearance of the polyribosomes in its cytoplasm. Reticulocytes leave the bone marrow and enter circulating blood. 4/2/2019 Page4
BIO 202IN: Human Anatomy and Physiology II 0.5%-1.5% of circulating RBCs are reticulocytes.
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