Chapter 28 - Structure and Function of the Hematologic System

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What is the most abundant class of plasma protein?
a. Globulin c. Clotting factors
b. Albumin d. Complement proteins
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Terms in this set (38)
What is the effect of low plasma albumin?
a. Clotting factors decrease, thus increasing the chance of prolonged bleeding.
b. Fewer immunoglobulins are synthesized, thus impairing the immune function.
c. Less iron is stored, thus increasing the incidence of iron deficiency anemia.
d. Osmotic pressure decreases, thus water moves from the capillaries to the
Which statement concerning erythrocytes is true?
a. Erythrocytes contain a nucleus, mitochondria, and ribosomes.
b. Erythrocytes synthesize proteins.
c. Erythrocytes have the ability to change shape to squeeze through microcirculation.
d. Erythrocyte colony-stimulating factor (E-CSF) stimulates erythrocytes.
What is the consequence of a splenectomy? a. The level of iron in circulation increases. b. Antibody production increases to improve immune function. c. The number of defective cells in circulation increases. d. The number of clotting factors increases.ANS: C Splenic absence from any cause (e.g., atrophy, traumatic injury, removal because of disease) has several secondary effects on the body, among them an increase in morphologically defective blood cells in the circulation, confirming the spleen's role in removing old or damaged cells. This description of the consequence of a splenectomy is not accurate for the other options.During an infection, why do lymph nodes enlarge and become tender? a. B lymphocytes proliferate. b. The nodes are inflamed. c. The nodes fill with purulent exudate. d. The nodes are not properly functioning.ANS: A The B lymphocyte proliferation in response to significant antigen (e.g., during infection) may result in lymph node enlargement and tenderness (reactive lymph node). This description is not accurate for the other options.Which blood cells are the chief phagocytes involved in the early inflammation process? a. Neutrophils c. Eosinophils b. Monocytes d. ErythrocytesANS: A Neutrophils are the chief phagocytes of early inflammation.Which blood cells are biconcave in shape and have the capacity to be reversibly deformed? a. Neutrophils c. Eosinophils b. Monocytes d. ErythrocytesANS: D The erythrocyte's size and shape are ideally suited to its function as a gas carrier. A red blood cell (RBC) is a small disk with two unique properties: (1) a biconcave shape and (2) the capacity to be reversibly deformed. These are characteristics not observed in any of the other options.Which hemoglobin is made from oxidized ferric iron (Fe3+) and lacks the ability to bind oxygen? a. Deoxyhemoglobin c. Methemoglobin b. Oxyhemoglobin d. Glycosylated hemoglobinANS: C Without reactivation by methemoglobin reductase, the Fe3+-containing hemoglobin (methemoglobin) cannot bind oxygen. This capability is not true of the other types of hemoglobin mentioned.The absence of parietal cells would prevent the absorption of an essential nutrient necessary to prevent which type of anemia? a. Iron deficiency b. Pernicious anemia c. Folic acid deficiency anemia d. Aplastic anemiaANS: B Dietary vitamin B12 is a large molecule that requires a protein secreted by parietal cells into the stomach (intrinsic factor [IF]) to transport across the ileum. Defects in IF production lead to decreased B12 absorption and pernicious anemia. The other options are not the result of this process.Which nutrients are necessary for the synthesis of DNA and the maturation of erythrocytes? a. Protein and niacin c. Cobalamin (vitamin B12) and folate b. Iron and vitamin B6 (pyridoxine) d. Pantothenic acid and vitamin CANS: C Cobalamin and folate are necessary for the synthesis of DNA and for the maturation of erythrocytes. The remaining options are not necessary for these processes to occur.Which nutrients are necessary for hemoglobin synthesis? a. Protein and niacin c. Cobalamin (vitamin B12) and folate b. Iron and vitamin B6 (pyridoxine) d. Pantothenic acid and vitamin CANS: B Iron and B6 (pyridoxine) are necessary for hemoglobin synthesis (see Table 27-6). The remaining options are not necessary for hemoglobin synthesis.Recycling of iron from erythrocytes is made possible by which of the following? a. Transferrin c. Apoferritin b. Hemosiderin d. ErythropoietinANS: A Transferrin is recycled (transferrin cycle) in the following manner: (1) the transferrin-iron complex binds to a transferring receptor on the erythroblast's plasma membrane; (2) the complex moves into the cell by receptor-mediated endocytosis; (3) iron is released (dissociated) from transferrin; and (4) the dissociated transferrin is returned to the bloodstream for reuse. The other options do not present an accurate description of the recycling of erythrocytic ironBy which structure are mature erythrocytes removed from the bloodstream? a. Liver c. Thymus b. Lymph nodes d. SpleenANS: D After approximately 100 to 120 days in the circulation, old erythrocytes are removed by tissue macrophages, primarily in the spleen.Which substance is used to correct the chronic anemia associated with chronic renal failure? a. Iron c. Cobalamin (vitamin B12) b. Erythropoietin d. FolateANS: B One of the most significant advances in the study of hematopoietic growth factors has been the development of erythropoietin for individuals with chronic renal failure. The other options are not associated with the treatment of chronic anemia.What is the role of thromboxane A (TXA2) in the secretion stage of hemostasis? a. Stimulates the synthesis of serotonin. b. Promotes vasodilation. c. Stimulates platelet aggregation. d. Promotes formation of cyclooxygenaseANS: C Platelet aggregation is primarily stimulated by TXA2 and adenosine diphosphate (ADP), which induce functional fibrinogen receptors on the platelet. The other options do not present an accurate description of the role of thromboxane A.Which of the following is the role of nitric oxide (NO) in hemostasis? a. Stimulates the release of fibrinogen to maintain the platelet plug. b. Stimulates the release of clotting factors V and VII. c. Causes vasoconstriction and stimulates platelet aggregation. d. Controls platelet activation through cyclic adenosine monophosphate (cAMP)-mediated signaling.ANS: D Endothelial cell NO synthase produces NO, which controls platelet activation through cAMP-mediated signaling. The other options do not present an accurate description of the role of NO in hemostasis.The drug heparin acts in hemostasis by which processes? a. Inhibiting thrombin and antithrombin III (AT-III) b. Preventing the conversion of prothrombin to thrombin c. Shortening the fibrin strands to retract the blood clot d. Degrading the fibrin within blood clotsANS: A Clinically administered heparin or heparin sulfate (on the surface of endothelial cells) binds to AT-III and induces a conformational change that greatly enhances its activity. Under normal conditions, the presence of endothelial cell heparin sulfate and available AT-III in the circulation cooperate to protect the vessels from the effects of spontaneously activated thrombin. The other options do not accurately describe the role heparin plays in hemostasis.What is plasmin's role in the clotting process? a. Stimulates platelet aggregation. b. Inhibits platelet adhesion and aggregation. c. Prevents the conversion of prothrombin to degrade the fibrin within blood clots. d. Degrades the fibrin within blood clotsANS: D Plasmin (also called fibrinase or fibrinolysin) is a serine protease that degrades fibrin polymers in clots. It is not capable of the functions described in the remaining options.What does polycythemia at birth indicate? a. Hypoxia in utero c. Congenitally absent spleen b. Dysfunctional bone marrow d. Dehydration in uteroANS: A The hypoxic intrauterine environment stimulates erythropoietin production in the fetus and accelerates fetal erythropoiesis, producing polycythemia (excessive proliferation of erythrocyte precursors) of the newborn. The other options are not related to polycythemia.Where are Kupffer cells located? a. Kidneys c. Pancreas b. Liver d. SpleenANS: B The liver macrophages are the only location for Kupffer cells.Where are Langerhans cells found? a. Skin c. Kidney b. Intestinal lining d. ThyroidANS: A Of the available options, only the skin is the location for Langerhans cells.What is the role of collagen in the clotting process? a. Initiates the clotting cascade. c. Stimulates fibrin. b. Activates platelets. d. Deactivates fibrinogen.ANS: B In the clotting process, collagen provides a particularly strong stimulus to activate platelets. Collagen does not bring about any of the other options.Which form of iron (Fe) can be used in the formation of normal hemoglobin? a. Fe+ c. Fe3+ b. Fe2+ d. Fe4+ANS: B It is crucial that the iron be correctly charged; only reduced ferrous iron (Fe2+) can bind oxygen in the lungs and release it in the tissues.Where are alveolar macrophages found? a. Skin c. Gastrointestinal tract b. Breasts d. LungsANS: D The lung is the only location for alveolar macrophages.What changes to the hematologic system is related to age? a. Platelet adhesiveness decreases. b. Lymphocyte function decreases. c. Cellular immunity increases. d. Erythrocyte reproduction accelerates.ANS: B Blood composition changes little with age. A delay in erythrocyte replenishment may occur after bleeding, presumably because of iron deficiency. Lymphocyte function appears to decrease with age. Particularly affected is a decrease in cellular immunity. Platelet adhesiveness probably increases with age.What is the function of erythrocytes? a. Tissue oxygenation c. Infection control b. Hemostasis d. Allergy responseANS: A Erythrocytes are solely responsible for tissue oxygenation.Which characteristics allow erythrocytes to function as gas carriers? (Select all that apply.) a. Permanent shape b. Compactness c. Reversible deformability d. Presence of hyperactive mitochondria e. BiconcavityANS: C, E A red blood cell (RBC) is a small disk with two unique properties: (1) a biconcave shape and (2) the capacity to be reversibly deformed. The other options are not relevant to the function of gas transport.Which statements about plasma proteins are correct? (Select all that apply.) a. Provide clotting factors. b. Transport triglycerides. c. Synthesize complement proteins. d. Create hydrostatic pressure. e. Transport cholesterol.ANS: A, B, C, E Plasma proteins do not create hydrostatic pressure. The other options are all accurate statements regarding plasma proteins.What are the primary anticoagulant mechanisms? (Select all that apply.) a. Antithrombin III b. Tissue factor pathway inhibitor c. Hematopoiesis d. Protein C e. PhagocytosisANS: A, B, D The major regulatory factors that control hemostasis reside where the greatest probability of clotting would occur—on the endothelial cell surface. The primary anticoagulant mechanisms include thrombin inhibitors (e.g., antithrombin III), tissue factor inhibitors (e.g., tissue factor pathway inhibitor), and mechanisms for degrading activated clotting factors (e.g., protein C). Hematopoiesis and phagocytosis are processes that are not related to anticoagulation.Which statements are true regarding the role of the endothelium in clot formation? (Select all that apply.) a. The surface of the endothelium produces plasma protease inhibitors. b. Plasma protease inhibitors assist in preventing clot formation. c. Thrombomodulin is a protein that is converted on the surface of endothelial cells. d. Protein A binds to thrombomodulin. e. Activated protein C enhances the adhesion ability of neutrophils.ANS: A, B, C The surface of the endothelium produces plasma protease inhibitors to resist clot formation. Thrombomodulin is a membrane thrombin-binding protein matter and is converted to activated protein C (see Figure 27-18) on the surface of endothelial cells. Protein C in the circulation binds to thrombomodulin. Activated protein C inhibits the adhesion of neutrophils to the endotheliumWhich statements characterize albumin? (Select all that apply.) a. Retains sodium to maintain water balance. b. Provides colloid osmotic pressure. c. Is synthesized in the liver. d. Is a carrier for drugs that have low water solubility. e. Is a small moleculeANS: B, C, D Albumin is a plasma protein produced by the liver. It serves as a carrier molecule for the normal components of blood, as well as for drugs that have low solubility in water (e.g., free fatty acids, lipid-soluble hormones, thyroid hormones, bile salts). Albumin molecules are large and do not diffuse freely through the vascular endothelium, thus they maintain the critical colloidal osmotic pressure (or oncotic pressure) that regulates the passage of water and solutes into the surrounding tissues (see Chapters 1 and 3).