Human Physiology Lecture 13 - Blood
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Questions and Answers

What role do healthy cells play in the process of hemostasis?

  • They convert blood into a solid gel during clot formation.
  • They activate the coagulation cascade directly.
  • They release substances like prostacyclin and nitric oxide. (correct)
  • They form a platelet plug to stop blood loss immediately.
  • What is the primary purpose of a platelet plug during hemostasis?

  • To form fibrin that stabilizes blood vessels.
  • To slow down blood loss until clot formation occurs. (correct)
  • To completely stop blood loss immediately.
  • To initiate the coagulation cascade.
  • What is the term for the conversion of blood into a solid mass during hemostasis?

  • Vasoconstriction
  • Coagulation (correct)
  • Fibrinolysis
  • Hemorrhage
  • Which substance is NOT involved in the coagulation cascade according to the information provided?

    <p>Prostacyclin (C)</p> Signup and view all the answers

    What initiates the coagulation cascade during the hemostatic process?

    <p>Damage to blood vessels (B)</p> Signup and view all the answers

    What role does thrombomodulin play in hemostasis?

    <p>It binds to thrombin and activates protein C. (A)</p> Signup and view all the answers

    Which condition is characterized by the deficiency of Factor VIII?

    <p>Hemophilia (C)</p> Signup and view all the answers

    What happens when low doses of aspirin are taken in relation to clotting?

    <p>It inhibits thromboxane A2 formation. (C)</p> Signup and view all the answers

    Which factor is involved in the enzymatic breakdown of fibrin during clot dissolution?

    <p>Plasmin (C)</p> Signup and view all the answers

    How does vitamin K deficiency affect the coagulation process?

    <p>It reduces synthesis of clotting factors. (C)</p> Signup and view all the answers

    What percentage of transported oxygen is bound to hemoglobin?

    <p>98.5% (C)</p> Signup and view all the answers

    What is the primary role of spectrin in erythrocytes?

    <p>Determines the shape of the erythrocyte (B)</p> Signup and view all the answers

    What is the life span of a mature red blood cell (RBC)?

    <p>120 days (C)</p> Signup and view all the answers

    Which of the following is a hematopoietic growth factor involved in erythrocyte production?

    <p>Erythropoietin (D)</p> Signup and view all the answers

    What is the primary site of erythrocyte synthesis in adults?

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

    What happens to old red blood cells in the body?

    <p>They are filtered by the spleen (D)</p> Signup and view all the answers

    What percentage of transported oxygen is dissolved in plasma?

    <p>1.5% (A)</p> Signup and view all the answers

    Which type of cell division occurs in mature red blood cells?

    <p>No cell division (B)</p> Signup and view all the answers

    What is the primary role of colony-stimulating factors and interleukins in leukocyte development?

    <p>They control the development of leukocytes from stem cells. (D)</p> Signup and view all the answers

    Which cellular component is NOT found in platelets?

    <p>Nucleus (A)</p> Signup and view all the answers

    What is the first step in the hemostasis process?

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

    What function does von Willebrand factor play in the formation of a platelet plug?

    <p>It enhances the stickiness of platelets for adherence to damaged vessels. (B)</p> Signup and view all the answers

    Which of the following substances is released from activated platelets to promote vasoconstriction?

    <p>Serotonin (B)</p> Signup and view all the answers

    In addition to platelets, what is a key component secreted during the formation of a platelet plug?

    <p>Von Willebrand factor (B)</p> Signup and view all the answers

    What is the primary physiological outcome of the activation of the sympathetic nervous system during hemostasis?

    <p>Enhanced resistance to blood flow via vasoconstriction. (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the characteristics of platelets?

    <p>They are smaller than erythrocytes and lack a nucleus. (C)</p> Signup and view all the answers

    What is the role of folic acid in erythrocyte production?

    <p>Necessary for DNA replication and cell proliferation (B)</p> Signup and view all the answers

    Which of the following is a function of neutrophils?

    <p>Phagocytosis of foreign material during infections (D)</p> Signup and view all the answers

    What condition is associated with a deficiency of Vitamin B12?

    <p>Pernicious anemia (C)</p> Signup and view all the answers

    How does iron deficiency affect hemoglobin levels in men?

    <p>Decreases hemoglobin content below 13 g/dL (C)</p> Signup and view all the answers

    Which type of leukocyte is primarily involved in combating parasitic infections?

    <p>Eosinophils (D)</p> Signup and view all the answers

    Which type of cell is a T lymphocyte known for?

    <p>Directly damaging foreign cells (C)</p> Signup and view all the answers

    What percentage of leukocytes in the blood are monocytes?

    <p>5% (A)</p> Signup and view all the answers

    What is the primary function of basophils in the immune response?

    <p>Contributing to allergic reactions (A)</p> Signup and view all the answers

    Flashcards

    Erythrocytes

    Red blood cells (RBCs), specialized cells crucial for oxygen transport, lacking a nucleus, mitochondria, and other organelles.

    Hemoglobin

    A protein in red blood cells that binds and transports oxygen throughout the body.

    Oxygen Transport

    The process of moving oxygen from the lungs to the tissues, primarily facilitated by hemoglobin in red blood cells.

    Erythropoiesis

    The process of red blood cell production in the bone marrow.

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    Red Blood Cell Life Cycle

    The lifespan and replacement of red blood cells. Healthy RBCs live ~120 days before being removed by the spleen.

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    Hematopoietic Growth Factors (HGFs)

    Cytokines that stimulate the production of blood cells, including red blood cells (erythrocytes).

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    Erythropoietin

    A specific hematopoietic growth factor crucial for stimulating red blood cell production.

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    Blood Composition

    Describes the components of blood, namely plasma, red blood cells, white blood cells, and platelets.

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    Dietary Iron for Erythrocytes

    Iron is crucial for hemoglobin production, a protein carrying oxygen in red blood cells.

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    Hemoglobin Content (Men)

    Normal hemoglobin levels in men's blood are between 13 and 18 grams per deciliter.

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    Hemoglobin Content (Women)

    Normal hemoglobin levels in women's blood are between 12 and 16 grams per deciliter.

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    Iron-Deficency Anemia

    A condition caused by insufficient iron intake, affecting red blood cell production.

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    Leukocytes: Neutrophils

    A type of white blood cell that primarily fights infections by consuming foreign material.

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    Leukocytes: Lymphocytes Function

    White blood cells that play a vital role in the immune response, producing antibodies and directly destroying foreign cells.

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    Essential Nutrient for DNA Replication

    Folic acid and vitamin B12 are needed for DNA replication, promoting cell production.

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    Pernicious Anemia Cause

    A type of anemia caused by deficiencies in vitamin B12, an essential nutrient for DNA replication.

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    Platelet Plug Formation

    The process where platelets adhere to exposed collagen at a damaged blood vessel, forming a temporary plug to slow bleeding.

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    Prostacyclin (PGI2)

    A chemical released by healthy blood vessel cells that inhibits platelet aggregation and promotes blood vessel dilation, preventing excessive clotting.

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    Blood Clot Formation (Coagulation)

    The process by which blood is converted into a solid gel (a clot or thrombus) to stop bleeding effectively, usually around a platelet plug.

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    Coagulation Cascade

    A series of enzymatic reactions involving plasma proteins, activated by tissue damage, leading to the formation of a blood clot.

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    Thrombin

    A key enzyme in the coagulation cascade that converts fibrinogen into fibrin, the essential protein for forming a blood clot.

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    Leukocyte Development

    Leukocytes, or white blood cells, are derived from hematopoietic stem cells, similar to red blood cells. They primarily mature in the bone marrow, with T lymphocytes undergoing final maturation in the thymus.

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    Hematopoietic Factors

    Colony-stimulating factors and interleukins are crucial for regulating the production and development of various blood cells, including leukocytes.

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    Platelets: What are they?

    Platelets are cell fragments derived from megakaryocytes. They are smaller than red blood cells and lack a nucleus, but contain essential components for blood clotting.

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    Hemostasis: The First Step

    Hemostasis refers to the processes that control bleeding. The first step is vascular spasm, where blood flow is restricted due to vasoconstriction.

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    Hemostasis: Second Step

    The second step in hemostasis is platelet plug formation. Platelets, also known as thrombocytes, are sticky and aggregate at the site of vessel damage.

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    Von Willebrand Factor (vWf)

    Von Willebrand factor is a crucial protein for platelet plug formation. It is secreted by megakaryocytes, platelets, and endothelial cells.

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    Platelet Adhesion

    Platelets adhere to the exposed collagen fibers in damaged vessels through vWf, forming the initial anchor for platelet aggregation.

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    Platelet Aggregation

    Activated platelets release serotonin, epinephrine, and ADP, which further increase their stickiness and trigger the production of thromboxane A2, resulting in more aggregation.

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    What inhibits the extrinsic pathway?

    Tissue factor pathway inhibitor (TFPI) is a protein secreted by healthy endothelial cells that specifically inhibits the extrinsic pathway of coagulation, preventing the formation of a blood clot.

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    How does thrombomodulin work?

    Thrombomodulin is a protein secreted by healthy endothelial cells that binds to thrombin, forming a complex that activates protein C, an anticoagulant that inhibits both the intrinsic and extrinsic clotting pathways.

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    How are clots dissolved?

    Plasmin, an enzyme, breaks down fibrin, the protein that forms the meshwork of a blood clot, dissolving the clot. Plasminogen is activated into plasmin by plasminogen activators, like tissue plasminogen activator (TPA).

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    What causes Hemophilia?

    Hemophilia is a genetic disorder caused by a deficiency in specific clotting factors, most commonly Factor VIII, leading to prolonged bleeding episodes.

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    How does aspirin work as an anticoagulant?

    Low doses of aspirin act as an anticoagulant by inhibiting the formation of thromboxane A2 (TXA2), reducing platelet aggregation and clot formation.

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    Study Notes

    Human Physiology Lecture 13 - Cardiovascular System - Blood

    • Objectives: Blood composition (excluding hematopoiesis), plasma, erythrocytes, leukocytes, platelets, and hemostasis. Textbook reference: Chapter 13, Section 13.2 (pp. 405-417, selected sections).

    Erythrocytes

    • 5 million/mm³
    • Lack nuclei, mitochondria, and organelles.
    • Biconcave disc shape, due to spectrin forming a spectrin net.

    Oxygen and Carbon Dioxide Transport

    • Hemoglobin greatly increases oxygen transport.
    • 98.5% of transported oxygen is bound to hemoglobin, 1.5% dissolved in plasma.
    • Hemoglobin also binds to carbon dioxide, hydrogen ions, and carbon monoxide.

    Life Cycle of Erythrocytes

    • Mature red blood cells (RBCs) cannot divide.
    • Short lifespan of 120 days.
    • Replacement rate of 2-3 million RBCs/second.
    • 200 billion RBCs are replaced daily.
    • Synthesized in red bone marrow (erythropoiesis).
    • Old RBCs are filtered by the spleen.

    Erythrocyte Production (Erythropoiesis)

    • Erythropoiesis occurs in bone marrow.
    • Dependent on hematopoietic growth factors (HGFs), specifically erythropoietin (EPO).
    • Leukocyte production also occurs in bone marrow, stimulated by colony-stimulating factors and interleukins.

    Dietary Requirements for Erythrocyte Production

    • Iron is a component of hemoglobin.
    • Normal hemoglobin levels:
      • Men: 13-18 g/dL
      • Women: 12-16 g/dL
    • Iron deficiency anemia is a condition where iron levels are insufficient.
    • Folic acid is necessary for DNA replication and cell proliferation.
    • Vitamin B12 is also necessary for DNA replication and cell proliferation and deficiency can lead to pernicious anemia.

    Hemostasis

    • Defined as the mechanisms to stop bleeding.
    • Three stages:
      1. Vascular spasm: Blood vessel constriction to minimize blood loss.
      2. Formation of a platelet plug: Platelets form a plug at the site of vessel damage.
      3. Formation of a blood clot: Blood is converted to a solid clot around the platelet plug.

    Platelets

    • Colorless cell fragments formed from megakaryocytes.
    • Smaller than erythrocytes; contain mitochondria, smooth endoplasmic reticulum, and cytoplasmic granules, but lack a nucleus.
    • Crucial for blood clot formation.

    Coagulation Factors in Clot Formation

    • Von Willebrand factor (vWF) is a key protein involved in platelet plug formation; secreted by megakaryocytes, platelets, and endothelial cells.
    • Coagulation factors involved in blood clot formation: (Intrinsic or Extrinsic pathways)
    • Involved in coagulation cascade, a series of proteolytic activations from peptide bond hydrolysis

    Factors Limiting Clot Formation

    • Anticoagulants: Proteins in plasma and on endothelial cell surfaces.
    • Tissue factor pathway inhibitor: Inhibits the extrinsic pathway.
    • Thrombomodulin: secreted by healthy endothelium, binds to thrombin, making an anticoagulant complex inhibiting intrinsic and extrinsic pathways
    • Plasmin dissolves clots enzymatically by breaking down fibrin.

    Role of Coagulation Factors in Clot Formation Disorders

    • Hemophilia: Genetic disorder caused by a deficiency of a clotting factor (e.g., Factor VIII).
    • Von Willebrand's disease: Reduced levels of vWF lead to reduced platelet plug formation.
    • Vitamin K deficiencies: Decrease the synthesis of clotting factors.

    Aspirin as an Anticoagulant

    • Low doses inhibit thromboxane A2 (TXA2) production, decreasing platelet aggregation.
    • High doses inhibit prostacyclin (PGI2) production, which is important in preventing the spread of the platelet plug and increasing likelihood of clot formation.

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    Description

    Explore the essential components of the cardiovascular system, specifically focusing on blood composition, erythrocytes, and the transport of oxygen and carbon dioxide. This quiz will help reinforce your understanding of hematology and erythropoiesis as outlined in Lecture 13. Reference your textbook for detailed sections.

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