Hematology Overview and Blood Functions

Hematology

• The study of blood, bone marrow, and the hemostasis system.
• Includes disorders of lymph nodes and related tissues.
• Encompasses a range of diseases including:
  • Genetic diseases (e.g., hemoglobinopathies, thalassemias)
  • Immune diseases (e.g., immune hemolytic anemia)
  • Malignancies (e.g., leukemias, lymphomas).
• Has played a crucial role:
  • Studying blood and its disorders
  • Understanding gene structure and function
  • Recognizing the importance of chromosomal abnormalities in malignancies
  • Advancing molecular biology of neoplasia

Blood

• Constitutes 6-8% of body weight in healthy adults.
• Total volume is approximately 5 liters.
• Distribution:
  • Systemic veins: 3 liters
  • Arterial system: 1 liter
  • Lungs: 1 liter
• Specific gravity: 1.050 - 1.060
• Viscosity: 2-5 times that of water
• Salinity: 0.85

Blood Functions

• Respiration:
  • Transport of oxygen from lungs to tissues.
  • Transport of CO2 from tissues to lungs for excretion.
• Nutrition:
  • Transports absorbed food materials from the digestive system to other parts of the body.
• Excretion:
  • Transports metabolic wastes to kidneys, lungs, skin, and intestines for removal.
• Acid-Base Balance:
  • Maintains normal blood pH (7.35-7.45).
• Water Balance:
  • Regulates water exchange between circulating fluid and tissue fluid.
• Temperature Regulation:
  • Distributes body heat; blood temperature is 38°C.
• Defense:
  • Provides defense against infection through white blood cells (WBCs) and circulating antibodies.
• Hormone Transport:
  • Transports hormones for metabolic regulation.

Blood Composition

• Consists of two phases:
  • Liquid phase (plasma):
    • Water, electrolytes (Na+, Ca++, HCO3-, Cl-), proteins, and other substances like sugar, fat, vitamins, and hormones.
  • Solid phase (formed elements):
    • Erythrocytes (red blood cells)
    • Leukocytes (white blood cells)
    • Platelets

Blood Components

• Plasma: 55% of blood volume

  • Serum: Plasma without fibrinogen, fibrin, Factor II, Factor V, Factor VIII. Rich in serotonin.
  • Fibrinogen: Key component of blood clotting.

• Solid Phase: 45% of blood volume

  • Red blood cells, white blood cells, and platelets.

Plasma

• Normal volume: 25-45 ml/kg of body weight.
• Specific gravity: 1.027.
• Components:
  • Approximately 92% water
  • 8% substances including proteins, ions, nutrients, gases, and waste products.
• Plasma proteins:
  • Albumin: 60% of plasma proteins; important for osmotic pressure of blood and water movement.
  • Globulin: 36% of plasma proteins; includes antibodies and complement (important in immune system).
  • Fibrinogen: 4% of plasma proteins; crucial for blood clot formation.

Plasma Volume

• Remains relatively constant.
• Water intake: Digestive tract
• Water loss: Kidneys, lungs, digestive tract, skin.

Composition of Plasma

• Electrolytes: Cations (Na+, K+, Mg++) and anions (Cl-, HCO3-, SO4, PO4).

• Proteins: Albumin, globulin, fibrinogen, transferrin, haptoglobin, hemopoietin.

• Other contents: Cholesterol, triglycerides, lipoproteins, glucose, urea, uric acid, iron, coagulation factors.

• Note: All plasma proteins are produced by the liver except for gamma-globulin, which is produced by plasma cells.

Functions of Plasma Proteins

• Osmotic pressure (oncotic pressure): Maintained at 25 mmHg, primarily by albumin. Hypoalbuminemia can lead to reduced oncotic pressure and edema.
• Transport system: Many substances are transported in the blood by plasma proteins:
  • Albumin: Ca+2, bilirubin, sulpha drugs.
  • Alpha-globulin: B12, thyroxin (T3), cortisol.
  • Beta-globulin: Cholesterol, lipids, insulin, vitamin A, PO4, K+.