Platelets and Hemostasis
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Questions and Answers

What is a distinguishing feature of lymphocytes?

  • They are large and contain abundant granules.
  • Their cytoplasm appears bluegray and foamy.
  • They have a kidney-shaped nucleus.
  • They possess a round and dark-staining nucleus. (correct)
  • What type of macrophage remains in a specific tissue, such as the lungs?

  • Wandering macrophages
  • Migratory macrophages
  • Fixed macrophages (correct)
  • Activated macrophages
  • What is the appearance of the cytoplasm of monocytes?

  • Clear with prominent vacuoles
  • Bluegray with a foamy appearance (correct)
  • Pink with coarse granules
  • Bright yellow with large granules
  • Which statement about the characteristics of lymphocytes is NOT true?

    <p>They possess visible granules under a light microscope.</p> Signup and view all the answers

    Monocytes differentiate into which type of cells once they leave the bloodstream?

    <p>Macrophages</p> Signup and view all the answers

    What is the primary function of platelets in the blood?

    <p>Promoting blood clotting</p> Signup and view all the answers

    Which component of hemostasis involves the immediate constriction of blood vessels?

    <p>Vascular spasm</p> Signup and view all the answers

    What is the typical lifespan of platelets in circulation?

    <p>5 to 9 days</p> Signup and view all the answers

    Which of the following is NOT a mechanism involved in reducing blood loss during hemostasis?

    <p>Blood vessel dilation</p> Signup and view all the answers

    How are aged and dead platelets removed from circulation?

    <p>By fixed macrophages in the spleen and liver</p> Signup and view all the answers

    What is the primary function of B cells in the immune system?

    <p>Destroying bacteria and inactivating their toxins</p> Signup and view all the answers

    Which type of cell primarily attacks viruses and fungi?

    <p>T cells</p> Signup and view all the answers

    How do platelets develop from megakaryocytes?

    <p>By splintering into 2000 to 3000 fragments</p> Signup and view all the answers

    What role does thrombopoietin play in platelet formation?

    <p>Acts on myeloid stem cells to develop into megakaryocytes</p> Signup and view all the answers

    What types of cells do Natural Killer (NK) cells attack?

    <p>A wide variety of infectious microbes and certain tumor cells</p> Signup and view all the answers

    What is the initial cell type involved in erythropoiesis?

    <p>Proerythroblast</p> Signup and view all the answers

    What happens to the proerythroblast during erythropoiesis?

    <p>It ejects its nucleus.</p> Signup and view all the answers

    What do reticulocytes retain during their development?

    <p>Mitochondria, ribosomes, and endoplasmic reticulum</p> Signup and view all the answers

    How long does it take for reticulocytes to develop into mature red blood cells?

    <p>1 to 2 days</p> Signup and view all the answers

    From where do reticulocytes enter the bloodstream?

    <p>Red bone marrow</p> Signup and view all the answers

    What role do neutrophils play in response to tissue damage?

    <p>They respond most quickly and use strong oxidants to combat bacteria.</p> Signup and view all the answers

    Which type of white blood cell is primarily responsible for intensifying inflammatory reactions?

    <p>Basophils</p> Signup and view all the answers

    What process characterizes the action of monocytes during an immune response?

    <p>They enlarge and differentiate into macrophages.</p> Signup and view all the answers

    How do eosinophils contribute to the immune defense?

    <p>They phagocytize antigen-antibody complexes and target parasitic worms.</p> Signup and view all the answers

    What is a common characteristic of both neutrophils and macrophages?

    <p>Both are active phagocytes responding to pathogens.</p> Signup and view all the answers

    What process describes the movement of white blood cells (WBCs) from the bloodstream into the tissue?

    <p>Emigration</p> Signup and view all the answers

    Which molecules on endothelial cells assist in the rolling of white blood cells along the vessel lining?

    <p>Selectins</p> Signup and view all the answers

    Which statement accurately describes the role of integrins in the emigration of WBCs?

    <p>They help WBCs to adhere to the endothelium.</p> Signup and view all the answers

    What is the primary reason different types of WBCs have varying signals for emigration?

    <p>WBCs respond to specific pathogens.</p> Signup and view all the answers

    Which of the following accurately describes the composition of MHC antigens?

    <p>They are unique to each individual, except identical twins.</p> Signup and view all the answers

    What occurs after a white blood cell sticks to the endothelium during emigration?

    <p>It squeezes between the endothelial cells to enter the tissue.</p> Signup and view all the answers

    What is the primary function of vascular spasm following damage to an artery?

    <p>To decrease blood loss temporarily</p> Signup and view all the answers

    Which of the following substances is NOT involved in platelet activation?

    <p>Fibrinogen</p> Signup and view all the answers

    What initiates the reflex that may contribute to vascular spasm?

    <p>Pain receptor activation</p> Signup and view all the answers

    During platelets’ release reaction, which of the following is a function of thromboxane A2?

    <p>Acting as a vasoconstrictor</p> Signup and view all the answers

    What role do activated platelets play during platelet plug formation?

    <p>They become activated and help recruit more platelets</p> Signup and view all the answers

    What is the primary stimulus for erythropoiesis?

    <p>Cellular oxygen deficiency</p> Signup and view all the answers

    Which of the following conditions can lead to hypoxia?

    <p>High altitude</p> Signup and view all the answers

    Which type of white blood cell is classified as a granular leukocyte?

    <p>Basophil</p> Signup and view all the answers

    Which vitamin deficiency can contribute to anemia?

    <p>Vitamin B12</p> Signup and view all the answers

    What defines the controlled condition in the regulation of erythropoiesis?

    <p>Amount of oxygen delivered to body tissues</p> Signup and view all the answers

    What color do the granules of eosinophils stain with acidic dyes?

    <p>Red-orange</p> Signup and view all the answers

    Which characteristic is unique to basophils compared to eosinophils?

    <p>Granules stain blue-purple</p> Signup and view all the answers

    Which statement about the nucleus of the eosinophil is true?

    <p>It has two lobes</p> Signup and view all the answers

    What type of granules do basophils possess?

    <p>Round, variable-sized granules</p> Signup and view all the answers

    What makes eosinophils eosinophilic?

    <p>Their granules stain with acidic dyes</p> Signup and view all the answers

    What is the characteristic lifespan of lymphocytes compared to other white blood cells?

    <p>They can live for months or years.</p> Signup and view all the answers

    Which of the following statements about leukocytosis is true?

    <p>It is a protective response that can occur during strenuous exercise.</p> Signup and view all the answers

    How are neutrophils commonly identified under a light microscope?

    <p>They possess a pale lilac color with small granules.</p> Signup and view all the answers

    What happens to the number of nuclear lobes in neutrophils as they age?

    <p>It increases to two to five lobes.</p> Signup and view all the answers

    Which condition is described as never being beneficial in terms of white blood cell levels?

    <p>Leukopenia</p> Signup and view all the answers

    Study Notes

    Platelets (Thrombocytes)

    • Normal range: 150,000 to 400,000 platelets per µl of blood
    • Shape: Irregular disc, 2-4 µm diameter, lacks a nucleus but contains vesicles
    • Vesicles store chemicals essential for coagulation (blood clotting)
    • Lifespan: 5 to 9 days; aged platelets are cleared by macrophages in the spleen and liver
    • Development involves thrombopoietin influencing myeloid stem cells to become megakaryocytes, which fragment to release platelets

    Hemostasis

    • Hemostasis is a series of processes to stop bleeding from damaged blood vessels
    • Characteristics of hemostatic response: quick, localized, and tightly regulated
    • Mechanisms for reducing blood loss:
      • Vascular spasm
      • Platelet plug formation
      • Blood clotting (coagulation)

    Agranular Leukocytes

    • Lack visible cytoplasmic granules under a light microscope
    • Lymphocyte Characteristics:
      • Nucleus: Round and dark-staining
      • Cytoplasm: Stains sky blue
      • Size classification: Large and small lymphocytes
    • Monocyte Characteristics:
      • Nucleus: Kidney-shaped or horseshoe-shaped
      • Cytoplasm: Blue-gray with a foamy appearance due to azurophilic granules
      • Monocytes differentiate into macrophages in tissues
    • Macrophages Types:
      • Fixed (tissue) macrophages: Reside in specific tissues
      • Wandering macrophages: Roam tissues to sites of infection

    Lymphocyte Function

    • Major players in the immune response:
      • B cells: Target and destroy bacteria and toxins
      • T cells: Attack viruses, fungi, cancer cells, and some bacteria
      • Natural Killer (NK) cells: Attack various infectious microbes and certain tumors

    White Blood Cells (WBCs)

    • Active phagocytes include:
      • Neutrophils: Respond quickly to bacterial infection using lysozymes and defensins
      • Monocytes: Arrive later but in greater numbers, differentiating into macrophages
    • Basophils:
      • Release granules (heparin, histamine, serotonin) at inflammation sites
      • Play a role in allergies and intensify inflammatory reactions
    • Eosinophils:
      • Release histaminase, phagocytize complexes, and combat parasitic infections

    WBC Emigration

    • WBCs leave the bloodstream via emigration (previously known as diapedesis)
    • Process involves rolling along the endothelium, adhering, and squeezing between endothelial cells
    • Signals for emigration vary by WBC type, involving selectins and integrins

    Erythropoiesis: Production of RBCs

    • Begins with proerythroblasts in red bone marrow, which synthesize hemoglobin
    • Proerythroblast divides, eventually ejecting the nucleus to become reticulocytes
    • Reticulocytes mature into RBCs within 1-2 days after entering circulation

    Vascular Spasm

    • Immediate contraction of smooth muscle in damaged blood vessels to limit blood loss for minutes to hours
    • Initiated by smooth muscle damage, platelet release substances, and pain reflexes

    Platelet Plug Formation

    • Adhesion: Platelets stick to damaged vessel areas (collagen fibers)
    • Activation: Platelet activation leads to projection extension and vesicle content release; ADP and thromboxane A2 recruit more platelets
    • Function of serotonin and thromboxane A2: Vasoconstriction to reduce blood flow

    Hypoxia and Feedback Mechanism

    • Hypoxia: Cellular oxygen deficiency, stimulating erythropoiesis
    • Conditions leading to hypoxia: High altitudes, pneumonia, anemia (iron, amino acids, vitamin B12), and circulatory problems
    • The primary controlled factor is oxygen delivery to tissues

    White Blood Cell Overview

    • WBCs (leukocytes) possess nuclei and organelles; do not contain hemoglobin
    • Classified as granular (neutrophils, eosinophils, basophils) and agranular (lymphocytes, monocytes)
    • Live for varying durations: a few days for most, but lymphocytes can last months to years
    • Leukocytosis: Increase in WBCs as a normal response to infection or stress
    • Leukopenia: Abnormally low WBC count, indicating potential health issues

    Granular Leukocytes Identification

    • Neutrophils: Multilobed nucleus, light-staining granules
    • Eosinophils: Dual-lobed nucleus, red-orange granules
    • Basophils: Dual-lobed nucleus, blue-purple granules

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    Description

    Learn about the structure and function of platelets, also known as thrombocytes, and the process of hemostasis, which stops bleeding when blood vessels are damaged.

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