BIOL 2304 Fall 2006Chapter 171 Chapter 17 - Blood

BIOL 2304 Fall 2006Chapter 172 I. hematocrit = % of blood volume occupied by erythrocytes average = 45% (average plasma volume = 55%)

BIOL 2304 Fall 2006Chapter 173 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)

BIOL 2304 Fall 2006Chapter 174 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

BIOL 2304 Fall 2006Chapter 175 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 CO 2

BIOL 2304 Fall 2006Chapter 176 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

BIOL 2304 Fall 2006Chapter 177 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

BIOL 2304 Fall 2006Chapter 178 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

BIOL 2304 Fall 2006Chapter 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

BIOL 2304 Fall 2006Chapter 1710 A. classification 1. granulocytes (neutrophils, eosinophils, basophils) cytoplasmic granules distorted, inactive nuclei phagocytic 2. agranulocytes (lymphocytes, monocytes) lack obvious granules in cytoplasm III. leukocytes

BIOL 2304 Fall 2006Chapter 1711 B. characteristics 1. neutrophils ( %) –nucleus has 2-6 lobes –cytoplasm stains light purple –phagocytize bacteria

BIOL 2304 Fall 2006Chapter eosinophils (1 - 4%) –nucleus has 2 lobes –cytoplasm stains red, orange or dark pink –phagocytize antigen-antibody complexes and fight parasitic worms

BIOL 2304 Fall 2006Chapter basophils (0 - 1%) –nucleus has 2 lobes (not visible) –cytoplasm stains dark blue/black –release histamine and other chemicals

BIOL 2304 Fall 2006Chapter lymphocytes ( %) –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

BIOL 2304 Fall 2006Chapter monocytes (4 - 8%) –nucleus horseshoe or kidney shaped –cytoplasm pale blue –largest WBC –become macrophages after migrating to c.t.

BIOL 2304 Fall 2006Chapter 1716 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

BIOL 2304 Fall 2006Chapter 1717 V. hematopoiesis occurs in the bone marrow (myeloid tissue) bone marrow is located inside bones there are two categories: –red - active –yellow - inactive

BIOL 2304 Fall 2006Chapter 1718 A. adult red marrow location: –proximal epiphyses of femur and humerus –axial skeleton –limb girdle bones

BIOL 2304 Fall 2006Chapter 1719 B. bone marrow histology –sinusoids (capillaries) –reticular cells, reticular fibers (stroma) –adipose tissue –multipotent blood stem cells (hemocytoblast) –immature blood cells

BIOL 2304 Fall 2006Chapter 1720 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

BIOL 2304 Fall 2006Chapter 1721 D. lineages 1. lymphoid stem cell lymphocytes 2. myeloid stem cell erythrocytes granulocytes monocytes megakaryocytes => platelets

BIOL 2304 Fall 2006Chapter 1722