Physiology L8 P2 White Blood Cells Quiz

White Blood Cells (Leucocytes)

• White blood cells (leukocytes) are crucial for the body's immune response.
• A normal total white blood cell count is 4500-11000 cells/mm³ (average 7000/mm³).
• Leukocytes are classified into two main groups: granulocytes and agranulocytes.

Types of Leukocytes

• Granulocytes:

  • Neutrophils: 60-70% of total leukocytes, primary defenders against bacterial invasion.
  • Eosinophils: 1-4% of total leukocytes, defend against parasites and play a role in allergic reactions.
  • Basophils: 0.25-0.5% of total leukocytes, release histamine and heparin, playing a role in allergic reactions.

• Agranulocytes:

  • Lymphocytes: 25-33% of total leukocytes, crucial for the immune system.
    • B lymphocytes: produce antibodies (humoral immunity).
    • T lymphocytes: directly destroy infected or cancerous cells (cellular immunity).
  • Monocytes: 2-6% of total leukocytes, mature into macrophages in tissues, highly phagocytic (engulf debris and microorganisms).

Functions of White Blood Cells

• Neutrophils: Phagocytic ("eat" invading bacteria and debris). Increased numbers during bacterial infections.
• Eosinophils: Kill parasites and involved in allergic reactions. Increased numbers during parasitic infections and allergic responses.
• Basophils: Release histamine and heparin; involved in allergic reactions.
• Lymphocytes: Crucial for adaptive (acquired) immunity. B cells produce antibodies, and T cells destroy infected/cancerous cells.
• Monocytes/Macrophages: Highly phagocytic, crucial for clearing infections and cell debris; settle in tissues.

Conditions with Increased White Blood Cells (Leucocytosis)

• Neutrophilia: Acute bacterial infection
• Eosinophilia: Parasitic infection, allergic reactions
• Basophilia: Allergies
• Lymphocytosis: Chronic bacterial infection, acute viral infection
• Monocytes and macrophages: Chronic bacterial infection

Conditions with Decreased White Blood Cells (Leucopenia)

• The presentation of lower than normal white blood cell counts signals a decrease in leukocytes

Leukemia

• Cancer of the blood and bone marrow.

Immunity

• Immunity is the body's ability to resist damage by organisms and toxins.
  • Innate (non-specific) immunity:
    • Inherited; present from birth
    • Examples: skin, acid in stomach, tissue neutrophils, macrophages
  • Acquired (specific) immunity:
    • Develops after exposure to a pathogen
    • Mediated by antibodies (humoral) or T cells (cellular)

Hemostasis (Stopping Bleeding)

• Hemostasis is the process of stopping bleeding after blood vessel damage.
  • Steps in Hemostasis:
    • Vascular spasm: Local vasoconstriction of the damaged blood vessel.
    • Platelet plug formation: Platelets adhere to exposed collagen fibers, aggregate, and form a temporary plug.
    • Blood coagulation: A cascade of clotting factors leads to the conversion of fibrinogen to fibrin, forming a stable blood clot to seal the damage.

Platelets (Thrombocytes)

• Platelets are cell fragments formed in bone marrow from megakaryocytes.
• Normal platelet count: 150,000-350,000/mm³.
• Life span: 7-10 days.
• Key role in hemostasis (stopping bleeding).
  • Adhere to damaged vessels
  • Aggregate to form a plug
• Removed from circulation by tissue macrophages

Platelet Aggregation

• Platelets adhere to exposed collagen fibers.
• Platelets begin to swell and change shape.
• Platelets become sticky and attract additional platelets, clumping together to form a platelet plug.
• This process is called platelet aggregation.

Blood Clotting

• A triggered chain reaction involving clotting factors results in blood clot formation, supporting the platelet plug and sealing the damaged vessel break
• Coagulation is the most powerful hemostatic mechanism.

Clot Formation Pathways

• Intrinsic pathway: Activated by factors inside blood vessels typically due to trauma
• Extrinsic pathway: Activated by factors outside blood vessels, typically by a damage to the external surfaces of the affected vessels and associated blood vessels
• Both pathways converge into a common pathway, culminating in fibrin formation and clot formation.
• Clotting time: normal is 3-6 minutes

Fibrin Formation

• Fibrinogen (a soluble plasma protein produced by the liver) is converted to fibrin (an insoluble thread-like molecule) by thrombin.
• Fibrin forms the meshwork of a blood clot.

Diseases Related to White Blood Cells & Platelets

• Hemophilia: Excessive bleeding due to deficiency in clotting factor VIII.
• Thrombocytopenic purpura: Deficiency of platelets, resulting in widespread hemorrhages.
• Thrombocytopenia -low platelet count, which predisposes the individual to bleeding

Test your knowledge on the types and functions of white blood cells. This quiz covers key concepts related to leukocytes, their classifications, and their role in the immune system. Understand the differences between granulocytes and agranulocytes and their significance in protecting the body.