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Unformatted text preview: PSIO 202 Human Anatomy and Physiology Lecture 2 Cardiovascular System: The Blood; Erythrocytes Objectives and Reading Assignment
Reading: Tortora, pages 695-99 Lecture Objectives
Describe the origin and production of the formed elements in the blood List the characteristics and functions of red blood cells Describe the structure and function of hemoglobin Understand how worn-out or damaged erythrocytes are destroyed and/or recycled Erythrocytes
Erythrocytes, or red blood cells (RBCs), are shaped like biconcave discs this increases the surface area available for oxygen binding average diameter of RBCs is about 8 uM they have no nucleus they are easily deformed they are filled with hemoglobin, a protein that carries oxygen. Normal Erythrocytes
about 8 uM in diameter About 2 uM thick No nucleus Filled with hemoglobin Easily deformed Hemoglobin
hemoglobin is composed of four large protein chains 2 alpha chains, and 2 beta chains a heme group is contained within each chain a heme group is a porphyrin ring that surrounds a single iron molecule. each iron molecule can bind one molecule of oxygen (O2) (4 molecules of O2/hemoglobin molecule) A Normal Hemoglobin Molecule Function of Hemoglobin
Each hemoglobin molecule can carry 4 oxygen molecules Oxygen is loaded onto hemoglobin in lung capillaries and transported to the tissue cells by the blood Hemoglobin also transports 23% of the total CO2 produced in tissue cells; the CO2 combines with amino acids in the globin portion of Hb Blood concentration of Hb in healthy humans
16-grams/100 ml of blood in men 14 g/100ml of blood in women The concentration of RBCs, or the "hematocrit", is equivalent to about 45 % of the total blood volume. Formation of Erythrocytes
Erythropoiesis refers to the formation of RBCs this occurs in the red bone marrow after birth, RBCs are formed from stem cells Stem cells differentiate into proerythroblasts The proerythroblasts then go through several intermediate stages to become reticulocytes When the reticulocytes reach maturity hemoglobin is produced and the nucleus is ejected, resulting in the formation of a mature erythrocyte Hemopoietic Growth Factors
Their role is to regulate differentiation & proliferation of blood cells Erythropoietin (EPO) produced by the kidneys increase RBC precursors Thrombopoietin (TPO) hormone from liver stimulates platelet formation Hemopoietic Growth Factors, Continued
Cytokines are local hormones of bone marrow produced by some marrow cells to stimulate proliferation in other marrow cells colony-stimulating factor (CSF) & interleukin stimulate WBC production Medical Usage of Growth Factors
Available through recombinant DNA technology
recombinant erythropoietin (EPO) very effective in treating decreased RBC production of end-stage kidney disease other products given to stimulate WBC formation in cancer patients receiving chemotherapy which kills bone marrow thrombopoietin helps prevent platelet depletion during chemotherapy RBC Life Cycle
Worn out cells removed by fixed macrophages in spleen & liver RBCs live only 120 days
wear out from bending to fit through capillaries no repair possible due to lack of nucleus Breakdown products are recycled Destruction and Recycling of RBCs
In macrophages of liver or spleen
globin portion broken down into amino acids & recycled heme portion split into iron (Fe+3) and biliverdin (green pigment) What Else Happens to the Heme Components?
transported in blood attached to transferrin protein stored in liver, muscle or spleen
attached to ferritin or hemosiderin protein transported to bone marrow for use in hemoglobin synthesis Biliverdin (green) converted to bilirubin (yellow)
bilirubin secreted by liver into bile
Bile is excreted via kidneys and intestine Life Cycle of Red Blood Cells ...
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- Fall '08