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The Cardiovascular System Notes

NURS 1114: The Cardiovascular System - Blood

Learning Objectives

  • Production and Maturation of White Blood Cells
    • Understand how white blood cells (WBCs) are produced and mature.
  • Platelet Structure, Function, and Production
    • Examine platelets' structure and their critical role in hemostasis.
  • Blood Clotting Reaction Sequences
    • Describe the sequences involved in blood clotting.
  • Importance of Blood Typing
    • Explain blood typing significance and the basis for ABO and Rh incompatibilities.

White Blood Cells Overview

  • Function: Fight infections
  • Characteristics:
    • Large in size
    • Nucleated cells
  • Phagocyte Definition: Cells that engulf and digest pathogens.

Types of Leukocytes (WBCs)

  • General Facts:
    • Only blood components that are complete cells.
    • Less numerous than red blood cells (RBCs); make up ~1% of total blood volume.
    • Can exit capillaries (diapedesis) and move in ameboid motion.
  • Leukocytosis: Excess WBCs (> 11,000 cells/mm³); often a response to infection.
  • Mnemonic for Differential WBC Count: Never Let Monkeys Eat Bananas (order: Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils).

Granulocytes

  1. Neutrophils:
    • Account for 40-70% of WBCs.
    • Multi-lobed nuclei, blue granules; major bacteria slayers.
  2. Eosinophils:
    • Account for 1-4% of WBCs.
    • Bilobed nuclei, red granules; combat parasites and modulate allergic reactions.
  3. Basophils:
    • Account for <1% of WBCs.
    • U/S-shaped nuclei, large granules containing histamine and heparin; involved in inflammatory responses.

Agranulocytes

  1. Lymphocytes:
    • Account for 20-45% of WBCs.
    • Contains B cells (produce antibodies) and T cells (kill infected cells).
  2. Monocytes:
    • Account for 4-8% of leukocytes; largest WBCs with kidney-shaped nuclei.
    • Differentiate into macrophages upon entering tissues (highly mobile phagocytes).

Formation and Maturation of Leukocytes

  • Hematopoiesis: Production originates from hemocytoblasts, which differentiate into:
    • Myeloid Stem Cells: Yield granulocytes (neutrophils, eosinophils, basophils) and monocytes.
    • Lymphoid Stem Cells: Yield lymphocytes.

Platelets

  • Function: Essential for clotting; live 2-4 days.
  • Composition: Fragments of megakaryocytes containing granules.
  • Activation: Involved in creating a temporary plug during hemostasis.

Hemostasis Overview

  • Phases of Hemostasis:
    1. Vascular Spasms: Vasoconstriction occurs immediately following vessel injury.
    2. Platelet Plug Formation: Platelets adhere to collagen and release substances to recruit more platelets.
    3. Coagulation: Blood changes from liquid to gel forming a clot.

Coagulation Stages

  1. Prothrombin Activator Formation: Triggered by intrinsic or extrinsic pathways.
  2. Thrombin Formation: Prothrombin is converted to thrombin.
  3. Fibrin Mesh Formation: Thrombin catalyzes fibrinogen to fibrin, creating a mesh that stabilizes the clot.

Blood Typing and Transfusion

  • ABO Blood Groups: Four main types (A, B, AB, O) based on antigens present on RBC surfaces.
  • Rh Factor: Presence of Rh factor leads to Rh+ status; important in pregnancy and transfusions.
  • Transfusion Reactions: Occur when mismatched blood is transfused, leading to hemolysis and complications.

Common Hematological Disorders

  • Leukemias: Blood cancers characterized by the overproduction of immature WBCs, can be acute or chronic.
  • Bleeding Disorders: Caused by deficiencies in platelets or clotting factors, treatments may include transfusions or factor replacement.
  • Hemolytic Disease of the Newborn: Occurs when an Rh- mother produces antibodies against Rh+ fetal blood, treatable with RhoGAM.

Conclusion

  • Understanding the cardiovascular system, particularly blood components and hemostatic processes, is critical for effective medical care.