General Physiology Lecture - Body Fluids

General Physiology Lecture - Body Fluids

• Topics Covered: Introduction, Body Fluids, Measurement of Body Fluid Volumes, Disturbances in Body Fluids
• Total Body Water (TBW): Approximately 60% of body weight. Expressed as a variable in liters.
• Intracellular Fluid (ICF): 40% of body weight, contained within cells.
• Extracellular Fluid (ECF): 20% of body weight, outside the cells.
  • Consists of interstitial fluid (most of ECF) and plasma.
• Blood Volume: Accounts for approximately 8% of body weight.
• Measurement Methods:
  • Indicator Dilution Method: Involves injecting a known initial volume of a substance (indicator). Samples are collected, and the concentration is calculated.
• Disturbances:
  • Dehydration: Loss of body fluid
    • Isotonic: Equal loss of water and electrolytes.
    • Hypertonic: Greater loss of water than electrolytes.
    • Hypotonic: Greater loss of electrolytes than water.
  • Overhydration: Gain of body fluid

Fluid Compartments

• ICF (Intracellular Fluid):
  • 2/3 of Total Body Water (TBW)
• ECF (Extracellular Fluid):
  • 1/3 of Total Body Water (TBW)
    • Plasma:
    • Interstitial Fluid: Fluid surrounding cells.
    • Transcellular Fluid: Fluids in specialised body compartments (e.g., synovial fluid, cerebrospinal fluid, pleural fluid.)
• Fluid Regulation: Important for maintaining health.
• Water Balance (Homeostasis): Body gains and loses water and electrolytes at equivalent rates

Disturbances In Body Fluid Compartments

• Primary Disturbance: The initial change and is mainly in the extracellular fluid volume (ECF).
• Osmolality: Measures the concentration of dissolved substances in a solution.
• Changes in ECF osmolarity can lead to shift in water:
  • Increased ECF osmolarity: Water moves from ICF to ECF.
  • Decreased ECF osmolarity: Water moves from ECF to ICF.

Measurement of Body Fluid Volumes

• Indicators: Various substances (e.g., deuterium oxide, mannitol) used to measure specific body fluid volumes. The chosen substance must meet specific conditions for accurate measurement and should not be metabolized by the body
• Methods: Indicator dilution techniques are used for accurate measurements.

This quiz covers key concepts of body fluids, including total body water, intracellular and extracellular fluid distributions, and the measurement of body fluid volumes. Additionally, it explores disturbances in body fluids such as dehydration and their types. Test your understanding of how body fluids play a vital role in physiology.