Body fluid compartments 1

Body Fluid Compartments

  • Presenter: Dr. Madiha Imran, Associate Prof Physiology

Importance of Water

  • Essential for survival: Vital for various physiological processes in the body.

Body Water

  • Proportion: Approximately 60% of body weight is water.

Water Intake

  • Sources:

    • Ingestion: 2100 ml/day

    • Metabolic Water (from oxidation of food): 200 ml/day

    • Total Intake: 2300 ml/day

  • Variability: Water intake is variable and can depend on factors such as climate, habits, and physical activity levels.

Water Output

  • Daily Loss: Total daily water loss is also approximately 2300 ml/day, distributed as follows:

    • Insensible Loss: 700 ml/day

    • Skin: 350 ml/day

    • Lungs: 350 ml/day

    • Sweat: 100 ml/day

    • Feces: 100 ml/day

    • Urine: 1400 ml/day

  • Balance: Body regulates water balance such that water intake equals water output, primarily controlled by the kidneys.

Internal and External Water Pools

  • Inputs and Outputs:

    • Internal Pool: Receives input from the external environment and includes excretion to the external environment.

    • Excretion: Occurs via ingestion, inhalation, or natural body functions such as sweating and urination.

    • Metabolism: Involves the production of water and its incorporation into complex molecular structures.

Body Fluid Composition

  • Body Water Content:

    • Total Body Water (TBW) in 70 Kg adult male is about 42 liters.

    • Percentage of Body Weight:

      • Adult Male: 60%

      • Adult Female: 50%

    • Factors influencing TBW:

      • Fat content (inversely related to body water)

      • Age

      • Gender

Tissue Water Content

  • Adipose Tissue: Driest tissue with about 20% water.

  • Other Tissues: Contain 60-80% water.

  • Age and Fat Relationship: As age and adipose tissue increase, the percentage of water content decreases in the body.

Body Fluids

  • Definition: Composed of water and dissolved solutes

    • Includes electrolytes which are crucial for various bodily functions.

Role of Kidneys

  • Regulation: Kidneys play a significant role in regulating body fluids and electrolytes.

Body Fluid Compartments Breakdown

  • Total Body Water:

    • Intracellular Fluid (ICF): 2/3 of TBW, approximately 28 liters.

    • Extracellular Fluid (ECF): 1/3 of TBW, approximately 14 liters.

      • Subcomponents of ECF:

        • Interstitial fluid: 11 liters

        • Plasma: 3 liters

        • Minor Compartment: Transcellular fluid, lymph

Composition of Intracellular versus Extracellular Fluid

  • Intracellular Fluid:

    • Comprises 75-80% water.

    • Major cations: K+, Mg2+.

    • Major anions: Proteins, organic phosphates (ATP, ADP).

    • pH range: 6.8 - 7.4.

  • Extracellular Fluid:

    • Water makes up about 93% of plasma.

    • Major cation: Na+.

    • Major anions: Cl-, HCO3-.

    • pH: 7.4.

Measurement of Body Fluid Compartments

  • Methods:

    • Indicator dilution method: Law of conservation of mass.

    • Use of indicators like tritium, deuterium, and antipyrine for TBW measurement.

    • Radioactive markers for ECF and plasma volumes.

Summary of Osmolarity and Tonicity

  • Osmolarity: Refers to total solute concentration in a solution. Measured in mOsm/L.

  • Tonicity: Refers to the effective osmolarity of a solution with respect to cellular membranes.

  • Types of Solutions:

    • Isotonic: Equal tonicity to ECF.

    • Hypotonic: Lower tonicity than ECF.

    • Hypertonic: Higher tonicity than ECF.

Calculations

  • For a healthy 70 kg adult male, plasma volume = 3300 ml.

  • Blood Volume Calculation: Blood volume = plasma volume × (100/100-Hct).

Conclusion and Acknowledgments

  • Thank you for attending the presentation.