Haematology Notes Lecrture 1

Learning Outcomes

• Describe the composition and physical characteristics of blood.

• Discuss the composition of plasma.

• Outline the different classes of plasma proteins.

• Explain the functions of blood components and apply them to pathological conditions.

• Explain what haematocrit is and what normal values represent.

• Describe the structure, function and production of erythrocytes.

• Discuss the life cycle of erythrocytes including their destruction.

• Discern between different classes and functions of leukocytes and apply this to explain which cells are responsible for protection against different types of pathogens.

Components of Blood

• Blood Composition:

  • Approximately 55% plasma and 45% formed elements (red blood cells, white blood cells, and platelets).

  • Blood Plasma: Clear, straw-coloured fluid; 55% of blood volume; contains no cellular components; high protein concentration; electrolytes, nutrients, and waste products.

• Formed Elements:

  • Erythrocytes (Red Blood Cells): Most abundant; responsible for oxygen and carbon dioxide transport via hemoglobin; lifespan of ~120 days; replaced at a rate of 1% daily.

  • Leukocytes (White Blood Cells): <1% of blood; major types include granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (monocytes and lymphocytes).

  • Platelets (Thrombocytes): Function in clotting, lifespan of 5-9 days; produced from megakaryocytes in the bone marrow.

Blood Characteristics

• Haematocrit (Hct): Measurement of the proportion of blood volume occupied by red blood cells; normal range is approximately 0.42-0.54 for males and 0.37-0.47 for females.

Plasma Composition and Functions

• Plasma Proteins (7% of total plasma): Normal levels range from 60-80g/L.

  • Albumin: Maintains osmotic pressure and transports insoluble molecules.

  • Globulins: Transport ions, hormones, lipids; play a role in immune function.

  • Fibrinogen: Critical for blood coagulation; acts as 'molecular glue'.

• Plasma Solutes (1.5% of total plasma):

  • Electrolytes: Maintain osmotic balance; important for nerve and muscle function. Common cations include Na+, K+, and Ca2+; anions include Cl- and HCO3-.

  • Nutrients: Glucose, amino acids, and lipids involved in metabolism.

  • Waste Products: Urea, creatinine, and bilirubin are products of metabolism that must be excreted.

Leukocyte Function and Types

• Leukocytes Overview: White blood cells split into three main types:

  • Granulocytes (neutrophils, eosinophils, basophils): Involved in inflammatory response and direct pathogen attack.

  • Lymphocytes: Comprising T-lymphocytes (cell-mediated immunity), B-lymphocytes (humoral immunity), and Natural Killer (NK) cells (targeting infected or cancerous cells).

  • Monocytes: Differentiate into macrophages in tissues; important for phagocytosis and inflammatory response.

• Neutrophils (50-72% of leukocytes): First responders against bacterial infections; lifespan of hours to days; utilize phagocytosis and produce reactive oxygen species for pathogen elimination.

• Eosinophils (2-4% of leukocytes): Attack larger parasites; lifespan around 5 days; contain digestive enzymes for extracellular digestion.

• Basophils (0.5-1% of leukocytes): Involved in allergic responses; release histamine which acts as a vasodilator; lifespan of hours to days.

Erythropoiesis and Lifespan

• Erythropoiesis: The process of generating mature red blood cells; regulated by erythropoietin (EPO).

• Erythrocyte Breakdown:

  • Hemoglobin is degraded in macrophages, globin is reused, heme is converted to bilirubin, and iron is recycled via transferrin back to the bone marrow. 10% are hemolyzed in circulation.

Blood Group Systems

• ABO System: Based on the presence of A and B antigens on red blood cell surfaces; incompatibility can lead to hemolytic reactions during transfusions.

• Rh Factor: Particularly the D antigen; Rh-positive individuals have the antigen while Rh-negative individuals lack it. Important for pregnancy and transfusion compatibility.

Key Terms Glossary

• Agglutination: Clumping of cells often in response to antibodies binding antigens.

• Antigen: Any substance that induces an immune response.

• Antibody: A protein produced that binds to a specific antigen.

• Anticoagulant: A substance that prevents blood coagulation.

• Erythrocyte: A red blood cell involved in oxygen transport.

1. Learning Outcomes

2. Components of Blood

   • Blood Composition

   • Blood Plasma

   • Formed Elements

3. Blood Characteristics

   • Haematocrit (Hct)

4. Plasma Composition and Functions

   • Plasma Proteins

   • Plasma Solutes

5. Leukocyte Function and Types

   • Leukocytes Overview

   • Neutrophils

   • Eosinophils

   • Basophils

6. Erythropoiesis and Lifespan

7. Blood Group Systems

   • ABO System

   • Rh Factor

8. Key Terms Glossary

   • Agglutination

   • Antigen

   • Antibody

   • Anticoagulant

   • Erythrocyte