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Lecture 8 (red blood cells)

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General physiology 8

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Lecture 8 (red blood cells)

  1. 1. RED BLOOD CELL
  2. 2. Blood: • Blood is the river of life that surges within us. • Transporting nearly everything that must be carried from one place to another. • Blood is a specialized connective tissue in which living blood cells, called the formed elements, are suspended in a nonliving fluid matrix called plasma. • Blood lacks the collagen and elastic fibers typical of other connective tissues, but dissolved fibrous proteins become visible as fibrin strands during blood clotting. • Blood is a sticky, opaque fluid with a characteristic metallic taste. • Blood is more dense than water and about five times more viscous, largely because of its formed elements. It is slightly alkaline, with a pH between 7.35 and 7.45.
  3. 3. Types of Blood: I. Red blood cells II. White blood cells A. Granular leukocytes (contain conspicuous granules that are visible under a light microscope after staining) 1. Neutrophils 2. Eosinophils 3. Basophils B. Agranular leukocytes (no granules are visible under a light microscope after staining) 1. T and B lymphocytes and natural killer (NK) cells 2. Monocytes III. Platelets
  4. 4. Blood Plasma: • Blood plasma is a straw-colored, sticky fluid. • Although it is mostly a) water (about 90%), plasma contains over 100 different b) dissolved solutes, including nutrients, gases, hormones, wastes and products of cell activity, proteins, and inorganic ions (electrolytes). • plasma proteins are the most abundant plasma solutes. • Plasma proteins serve a variety of functions, but they are not taken up by cells to be used as fuels or metabolic nutrients as are most other organic solutes, such as glucose, fatty acids, and amino acids.
  5. 5. RED BLOOD CELLS (ERYTHROCYTES) • Transport hemoglobin, which, in turn, carries oxygen from the lungs to the tissues. • In some animals, hemoglobin circulates as free protein in the plasma and is not enclosed in RBCs. • Contain a large quantity of carbonic anhydrase, an enzyme that catalyzes the reversible reaction between carbon dioxide (CO2) and water to form carbonic acid (H2CO3). • An excellent acid-base buffer. • Determination of blood group. • Normal RBCs, are biconcave disks having a mean diameter of about 7.8 micrometers and a thickness of 2.5 micrometers at the thickest point and 1 micrometer or less in the center. • The shapes of RBCs can change remarkably as the cells squeeze through capillaries.
  6. 6. PROPERTIES OF RED BLOOD CELLS: • ROULEAUX FORMATION: • the RBCs pile up one above another like the pile of coins. • SPECIFIC GRAVITY: • 1.092 to 1.101. • PACKED CELL VOLUME (hematocrit value): • 45% of the blood and the plasma volume is 55%. • SUSPENSION STABILITY
  7. 7. • Concentration of Red Blood Cells in the Blood: • In healthy men, the average number of RBCs per cubic millimeter is 5,200,000; in women, it is 4,700,000. • Quantity of Hemoglobin in the Cells: • The whole blood of men contains an average of 15 grams of hemoglobin per 100 milliliters; for women, it contains an average of 14 grams per 100 milliliters. • Each gram of hemoglobin can combine with 1.34 ml of oxygen if the hemoglobin is 100 percent saturated. • In a normal man a maximum of about 20 milliliters of oxygen can be carried in combination with hemoglobin in each 100 milliliters of blood, and in a normal woman 19 milliliters of oxygen can be carried.
  8. 8. PRODUCTION OF RED BLOOD CELLS: • In the early weeks of embryonic life, primitive, nucleated RBCs are produced in the yolk sac. • During the middle trimester of gestation, the liver is the main organ for production of RBCs, but reasonable numbers are also produced in the spleen and lymph nodes. • Then, during the last month or so of gestation and after birth, RBCs are produced exclusively in the bone marrow. Relative rates of red blood cell production in the bone marrow of different bones at different ages.
  9. 9. Genesis of Blood Cells:
  10. 10. Stages of Differentiation of Red Blood Cells:  Erythropoiesis, the production of RBCs starts on the red bone marrow with a precursor cell called a proerythorblast.  The proerythroblast divides several times producing cells that begin to synthesize hemoglobin.  Ultimately, a cell near the end of the development sequence ejects its necleus and becomes (reticulocyte).  They pass from red bone marrow into blood stream.  Reticulocytes develop into mature RBCs, with in 1 to 2 days after their release from red bone marrow.
  11. 11. Erythropoietin: • Erythropoietin Is Formed Mainly in the Kidneys 90%. • 10% of the normal erythropoietin formed in other tissues (mainly in the liver). • Erythropoietin Regulates Red Blood Cell Production. • Tissue Oxygenation Is the Most Essential Regulator of Red Blood Cell Production. • Erythropoietin Stimulates Production of Proerythroblasts from Hematopoietic Stem Cells.
  12. 12. • Maturation of Red Blood Cells Requires Vitamin B12 (Cyanocobalamin) and Folic Acid.
  13. 13. FACTORS NECESSARY FOR ERYTHROPOIESIS: • GENERAL FACTORS: I. Erythropoietin II. Thyroxine III. Hemopoietic growth factors IV. Vitamins (B,C,D,E). • MATURATION FACTORS: I. Vitamin B12. II. intrinsic factor. III. folic acid. • HEMOGLOBIN FORMATION FACTORS: I. proteins and amino acids. II. Iron. III. Copper. IV. Cobalt and nickel V. Vitamins: Vitamin C, riboflavin, nicotinic acid and pyridoxine.
  14. 14. HEMOGLOBIN FORMATION: • Synthesis of hemoglobin begins in the proerythroblasts and continues even into the reticulocyte stage of the RBCs.
  15. 15. • Hemoglobin Combines Reversibly With Oxygen: means that the iron part of the HB does not tightly bind to O2 instead they bind as a loose that can be released if the tissue needs O2.
  16. 16. IRON METABOLISM: • Because iron is important for the formation not only of hemoglobin but also of other essential elements in the body (e.g., myoglobin, cytochromes, cytochrome oxidase, peroxidase, and catalase). • The total quantity of iron in the body averages 4 to 5 grams. A. 65% in hemoglobin. B. 4% in myoglobin. C. 1% in the form of the various heme compounds that promote intracellular oxidation. D. 0.1% protein transferrin in the blood plasma. E. 15 to 30% is stored in the reticuloendothelial system and liver parenchymal cells, principally in the form of ferritin.
  17. 17. Transport and Storage of Iron:
  18. 18. THE LIFE SPAN OF RED BLOOD CELLS IS ABOUT 120 DAYS:
  19. 19. • ANEMIAS: means deficiency of hemoglobin in the blood. • POLYCYTHEMIA: the RBC count may be 7 to 8 million/mm3.

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