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Chapter 17 - Blood

Chapter 17 - Blood. I. hematocrit. = % of blood volume occupied by erythrocytes average = 45% (average plasma volume = 55%). to determine the hematocrit, a small tube of blood is collected: BLOOD then spun in a centrifuge for 5 minutes: PLASMA BLOOD

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Chapter 17 - Blood

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  1. Chapter 17 - Blood Chapter 17

  2. I. hematocrit • = % of blood volume occupied by erythrocytes • average = 45% (average plasma volume = 55%) Chapter 17

  3. to determine the hematocrit, a small tube of blood is collected: BLOOD then spun in a centrifuge for 5 minutes: PLASMA BLOOD erythrocytes are heavier than plasma and are packed in the bottom of the tube plasma is separated from formed elements a special scale is used to determine the relative volume occupied by the erythrocytes compared to total blood volume (see previous slide) Chapter 17

  4. II. erythrocytes • A. physical characteristics • 6 - 8 mm diameter • biconcave discs • more surface area than spherical cells • more flexible and less fragile • no nuclei or organelles • filled with hemoglobin Chapter 17

  5. B. hemoglobin • each molecule of Hb is made of 4 subunits • each subunit contains 1 peptide and 1 heme • normal adult Hb has 2 alpha and 2 beta peptides • each heme contains one • iron atom • the peptide • carries CO2 Chapter 17

  6. C. average lifespan of a RBC = 100 to 120 days • old RBCs are removed from circulation by phagocytes (spleen, liver, bone marrow) • some components are recycled • amino acids • Fe (stored in liver) • the remainder of the heme group is converted to bilirubin and excreted in bile Chapter 17

  7. D. disorders • 1. anemia = reduced ability of blood to carry oxygen • NOT always characterized by low red blood cell count or low hematocrit • a. iron deficiency • b. vitamin B12 deficiency / pernicious anemia caused by lack of intrinsic factor production in stomach Chapter 17

  8. c. aplastic anemia due to destruction of stem cells in bone marrow (radiation, cancer drugs, environmental toxins) • d. hemolytic anemia is caused by destruction of red blood cells • e. hemorrhagic anemia is caused by blood loss • f. genetic disorder causing abnormal hemoglobin Chapter 17

  9. 2. polycythemia = high RBC count • a. primary - bone marrow cancer • b. secondary • caused by: • adaptation to increased activity or altitude • dehydration • excess secretion of erythropoietin • effect = increased blood viscosity Chapter 17

  10. III. leukocytes • A. classification • 1. granulocytes (neutrophils, eosinophils, basophils) • cytoplasmic granules • distorted, inactive nuclei • phagocytic • 2. agranulocytes (lymphocytes, monocytes) • lack obvious granules in cytoplasm Chapter 17

  11. B. characteristics • 1. neutrophils (40 - 70%) • nucleus has 2-6 lobes • cytoplasm stains light purple • phagocytize bacteria Chapter 17

  12. 2. eosinophils (1 - 4%) • nucleus has 2 lobes • cytoplasm stains red, orange or dark pink • phagocytize antigen-antibody complexes and fight parasitic worms Chapter 17

  13. 3. basophils (0 - 1%) • nucleus has 2 lobes (not visible) • cytoplasm stains dark blue/black • release histamine • and other • chemicals Chapter 17

  14. 4. lymphocytes (20 - 45%) • nucleus round, dark, takes up most of cell • cytoplasm seen as thin rim of light blue • about same size as RBCs • functionally divided into 2 categories: • B cells make antibodies • T cells attack foreign, cancer and virus-infected cells Chapter 17

  15. 5. monocytes (4 - 8%) • nucleus horseshoe or kidney shaped • cytoplasm pale blue • largest WBC • become macrophages after migrating to c.t. Chapter 17

  16. IV. thrombocytes • fragments of cytoplasm enclosed by plasma membrane • cytoplasm contains secretory granules • involved in hemostasis • form platelet plugs • secrete chemicals that enhance blood coagulation Chapter 17

  17. V. hematopoiesis • occurs in the bone marrow (myeloid tissue) • bone marrow is located inside bones • there are two categories: • red - active • yellow - inactive Chapter 17

  18. A. adult red marrow location: • proximal epiphyses of femur and humerus • axial skeleton • limb girdle bones Chapter 17

  19. B. bone marrow histology • sinusoids (capillaries) • reticular cells, reticular fibers (stroma) • adipose tissue • multipotent blood stem cells (hemocytoblast) • immature blood cells Chapter 17

  20. C. stem cell divides by mitosis to form two daughter cells • one daughter cell becomes the new stem cell • one daughter cell differentiates • this daughter cell becomes the new stem cell • this daughter cell differentiates into a formed element Chapter 17

  21. D. lineages • 1. lymphoid stem cell • lymphocytes • 2. myeloid stem cell • erythrocytes • granulocytes • monocytes • megakaryocytes => platelets Chapter 17

  22. Chapter 17

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