MD137 Haematology Lecture 1

MD137 Haematology - Lecture 1

• Course: MD137 Haematology
• Lecture: 1, Functions & Composition of Blood
• Lecturer: Dr. Louise Horrigan, Physiology
• Email: [email protected]

Learning Objectives

• Blood functions
• Blood constituents
• Plasma characteristics
• Formed element characteristics

Functions of Blood

• Transport of O₂ and CO₂
• Transport of nutrients and waste
• Transport of hormones
• Maintenance of homeostasis
• Heat regulation
• Regulation of pH
• Immunity (white blood cells, antibodies)
• Haemostasis (blood clotting balance)

Properties of Blood

• Constitutes approximately 8% of body weight (Female 4-5L, Male 5-6L)
• pH: 7.35 - 7.45
• Osmolarity: 285 - 295 mOsm/L
• Viscosity: 3.5 – 5.5 times that of water (whole blood)
• Density/specific gravity: 1.05g/ml
• Composition: Formed elements (45%) and plasma (55%)

Blood Collection and Separation

• Blood collected in vacutainers with anticoagulants (EDTA, citrate, or heparin)
• Centrifugation separates blood into:
  • Plasma (55% of total blood volume)
  • Buffy coat (leukocytes & platelets, <1% of total blood)
  • Erythrocytes (red blood cells, 45% of total blood)

Haematocrit (PCV)

• Percentage of blood occupied by red blood cells (RBCs)
• Normal values:
  • Females: 0.37 - 0.47
  • Males: 0.42 - 0.52

Constituents of Blood

• Plasma: Approximately 55% of blood
  • Water (91-93%)
  • Proteins (6-8%)
  • Other constituents (~1400 identified)
    • Nutrients (glucose, lipids, amino acids)
    • Nitrogenous wastes
    • Gases
    • Electrolytes
    • Hormones
• Formed elements: Approximately 45% of blood
  • White blood cells (leukocytes)
  • Red blood cells (erythrocytes)
  • Platelets

Plasma Proteins

• Albumin: ~60% (contributes to viscosity, fluid balance, carrier for hormones/drugs)
• Globulins: ~36% (transport lipids, vitamins, hormones, antibodies)
• Fibrinogens: ~4% (blood clotting)
• Others: ~1% (regulatory proteins)

Formed Elements: Specifics

• Erythrocytes (red blood cells):
  • 4.3-5.9 million/µL (males)
  • 3.5-5.5 million/µL (females)
• Leukocytes (white blood cells):
  • 4,500-11,000/µL
• Thrombocytes (platelets):
  • 150,000-400,000/µL

Thrombocytes (platelets)

• Arise from megakaryocytes
• 1 megakaryocyte releases over 1000 platelets
• 1.5-3µm in diameter
• No nucleus but have mitochondria
• Lifespan of approximately 10 days
• Intracellular granules hold proteins/factors
• Prevent blood loss
• Wound healing/blood vessel integrity
• Immune functions

Erythrocytes (red blood cells): Structure/Function

• Biconcave discs for large surface area of gas diffusion
• 6-8 µm in diameter, 2.5 µm thick
• Lack of a nucleus
• Lack of mitochondria (anaerobic energy production)
• Lifespan of 120 days

Erythrocytes: Functions

• Carriage of O₂ (99% bound to haemoglobin)
• Carriage of CO₂ (10% dissolved, 30% bound to plasma proteins, 60% as bicarbonate)
• Regulation of pH

Regulation of Blood pH (Bicarbonate System)

• Cytoplasm contains carbonic anhydrase
• Carbonic acid quickly dissociates into bicarbonate and hydrogen ions(CO₂ + H₂O ↔ H₂CO₃ ↔ HCO₃⁻ + H⁺)
• Principle of Le Chatelier: High CO₂ shifts to right, producing H⁺ ions

Regulation of Blood pH (Hemoglobin)

• Most H⁺ produced from carbonic acid binds to haemoglobin
• HCO₃⁻ can leave the cell to act as a buffer in the plasma.
• HCO₃⁻/Cl⁻ antiporter carries Cl⁻ into the cell and HCO₃⁻ out (chloride shift).
• Haemoglobin directly binds some CO₂

Leukocytes (White Blood Cells)

• Different types identified by size, shape of nucleus, and granularity.
• Differential white blood cell count (Total WBC count = 4,500 – 10,000 cells/µL)
• Different types are described (neutrophils, eosinophils, basophils, lymphocytes, and monocytes.)

Relative Abundance in Blood

Detailed percentages of types of leukocytes in the blood.

Granulocytes vs. Agranulocytes

• Granulocytes contain granules
• Agranulocytes do not contain granules

Neutrophils

• Large cells (2-3 days)
• Primary function is phagocytosis
• Travel quickly from blood to infection site
• Present in tissue during acute inflammation

Eosinophils, Basophils, Lymphocytes, and Monocytes

• Specific functions and characteristics for each

Summary of Main Points

• Blood performs many functions besides oxygen and carbon dioxide transport
• Properties of blood (pH, osmolarity) are tightly regulated
• Blood composed of formed elements (45%) and plasma (55%)
• Hematocrit is the proportion of blood occupied by erythrocytes (higher in males)
• Plasma composed of water, proteins & other constituents
• Plasma proteins important in transport and fluid balance
• RBCs have structure for O₂ and CO₂ transport, pH regulation
• WBCs play a role in immune defense
• Platelets are essential in blood clotting

Explore the foundational concepts of blood in this first lecture of the MD137 Haematology course. Learn about the various functions and composition of blood, including the characteristics of plasma and formed elements. This quiz will test your knowledge on blood transport mechanisms and its vital properties.