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.