Topic 9

Chapter 10: Hematology Overview

Definition

  • Hematology: The study of blood.

Composition and Volume of Whole Blood

  • Blood transports:

    • Nutrients

    • Wastes

    • Hormones

    • Gases (Oxygen & Carbon Dioxide)

  • Blood is classified as:

    • The only fluid tissue in the human body.

    • A connective tissue.

  • Components of blood:

    • Living cells (formed elements)

    • Nonliving matrix (plasma).

  • Blood volume in a healthy man: 5–6 liters (6 quarts).

  • Blood constitutes about 8% of body weight.

Blood Plasma

Composition

  • Plasma accounts for 55% of blood volume:

    • Water: 90% of plasma volume, serves as a solvent.

    • Salts (electrolytes)

    • Nutrients, gases, hormones, and plasma proteins:

      • Albumin: Regulates osmotic pressure, transports molecules, pH buffer.

      • Fibrinogen: Clotting of blood.

      • Globulins: Defense (antibodies) and lipid transport.

Functions

  • Plasma plays a crucial role in:

    • Transportation of nutrients, waste, respiratory gases, and hormones.

    • Maintaining pH balance and osmotic pressure.

pH Regulation

  • Normal blood pH: 7.35 to 7.45; imbalances can lead to acidosis (pH < 7.35) or alkalosis (pH > 7.45).

  • Respiratory system and kidneys regulate pH through CO2 transport and ion reabsorption.

Formed Elements

Types of Cells

  • Erythrocytes (Red Blood Cells):

    • Carry oxygen to tissues

    • Lifespan of approximately 100–120 days.

    • Contain hemoglobin which binds oxygen.

  • Leukocytes (White Blood Cells):

    • Immune defense; normal range: 4,800 to 10,800 WBCs/mm³ of blood.

  • Platelets (Thrombocytes):

    • Involved in clotting, formed from megakaryocytes.

Leukocyte Types

  1. Granulocytes;

    • Neutrophils: Phagocytize pathogens.

    • Eosinophils: Attack parasitic worms and play roles in allergies.

    • Basophils: Release histamine during inflammation.

  2. Agranulocytes;

    • Lymphocytes: B cells (antibody production) and T cells (viral defense).

    • Monocytes: Become macrophages to clean up debris.

Homeostatic Imbalances

Anemia

  • Defined as a decrease in oxygen-carrying capacity.

  • Types:

    • Iron-deficiency anemia: Due to lack of iron in diet.

    • Pernicious anemia: Vitamin B12 deficiency.

    • Aplastic anemia: Due to bone marrow failure.

Polycythemia

  • Excess RBCs leading to increased blood viscosity and impaired circulation; causes include bone marrow cancer or high altitude.

Leukopenia and Leukocytosis

  • Leukopenia: Abnormally low WBC count (< 4,000 cells/mm³).

  • Leukocytosis: High WBC count (> 11,000 cells/mm³), indicating infection.

Hematopoiesis

  • The process of blood cell formation occurring in red bone marrow from hemocytoblasts.

  • Erythropoietin, produced by kidneys in response to low oxygen, regulates RBC production.

Hemostasis

Definition

  • Stoppage of bleeding from blood vessel injury involving:

    • Vascular spasms

    • Platelet plug formation

    • Coagulation (blood clotting).

Mechanisms of Hemostasis

  1. Vascular Spasms: Reduce blood loss through vasoconstriction.

  2. Platelet Plug Formation: Platelets adhere and release chemicals to attract more platelets.

  3. Coagulation: Involves the conversion of prothrombin to thrombin, forming a fibrin mesh that stabilizes the clot.

Blood Typing and Transfusion Reactions

Blood Groups

  • Blood contains antigens (A, B, Rh) and antibodies that determine compatibility.

  • Type O is the universal donor; Type AB is the universal recipient.

Rh Factor

  • Rh-positive (Rh+) individuals have the D antigen; problems arise when Rh- mothers bear Rh+ children due to possible hemolytic disease of the newborn.

  • RhoGAM can prevent issues in subsequent pregnancies.

Conclusion

  • Understanding blood composition and its functions is essential for diagnosing and treating hematological conditions.