CFR.4 Blood Cells

Components of Blood

  • Whole Blood: Consists of plasma and cellular components:

    • Plasma:

      • Proteins: Albumins, Globulins, Fibrinogen

      • Water, Salts, Dissolved gases

      • Hormones and Clotting factors

    • Cell Components:

      • Red Blood Cells (Erythrocytes)

      • White Blood Cells (Leukocytes): Granular and Agranular types

      • **Platelets (Thrombocytes) **

Types of Blood Cells

1. Leukocytes (White Blood Cells)

  • Function: Part of the body's defense system; capable of amoeboid movement.

  • Composition: About 1% of blood cells, with around 7,000/ml in human blood.

  • Formed in red bone marrow and lymphoid tissues.

  • Types:

    • Agranulocytes

    • Granulocytes

2. Erythrocytes (Red Blood Cells)

  • Anucleate and biconcave in shape, optimized for oxygen transport.

  • Normal count: 5.2 million/ml in males, 4.7 million/ml in females.

  • Circulate for approximately 120 days before removal by the liver and spleen.

3. Thrombocytes (Platelets)

  • Key role in hemostasis (control of bleeding) through clot formation.

  • Anucleate cell fragments derived from megakaryocytes.

  • Life span of about 8 days in the bloodstream.

Types of Leukocytes

Agranulocytes

  • Lymphocytes:

    • Smallest WBCs (30% of leukocytes).

    • Types: T-lymphocytes (cellular immunity) and B-lymphocytes (humoral immunity).

  • Monocytes:

    • Largest WBCs (5% of leukocytes).

    • Ability to phagocytose and transform into macrophages in tissues.

Granulocytes

  • Neutrophils:

    • Most abundant (62%); involved in phagocytosis.

  • Eosinophils:

    • Present in parasitic infections and allergic reactions.

  • Basophils:

    • Rarest type (0.4%); involved in allergic responses.

Haemopoiesis (Blood Cell Formation)

  • Blood cells derived from a common multipotent stem cell (haemocytoblast).

  • Sites of haemopoiesis evolve from the liver and spleen to red bone marrow.

  • Hormone erythropoietin (EPO) regulates erythrocyte production, triggered by hypoxia, blood loss, or anemia.

Blood Clotting

Processes Involved

  • Intrinsic Pathway: Initiated by damage within blood vessels, involves platelets.

  • Extrinsic Pathway: Initiated by external tissue damage.

  • **Both pathways converge on the formation of thrombin and fibrin.

Mechanism of Clot Formation

  • Role of fibrinogen in forming a clot through complex interactions and calcium ions.

  • Factors involved in clotting cascade include prothrombin, thrombin, and various clotting factors.

Haemophilia

  • Definition: A genetic disorder characterized by abnormal bleeding due to deficiencies in clotting factors.

  • Types:

    • Hemophilia A: Deficiency in clotting factor VIII (80% of cases).

    • Hemophilia B: Deficiency in clotting factor IX (20% of cases).

  • Symptoms of increased bleeding after trauma or spontaneously.

References

  • Biology by Solomon – Chapter 44

  • Human Biology by Chiras – Chapters 6 & 7

Additional Information

  • For further assistance, contact: Prof Warren Thomas

    • Email: wathomas@rcsi-mub.com