ECF | Anatomy2Medicine
ECF,NEET PG,HEART,

ECF

 

 

  • The distribution of Na+ and K+ is maintained by Na+-K+-ATPBody Fluids

 

        • Humans are composed primarily of water.
        • Body composition depends on age and sex
        • Total body water (TBW) is divided into two major compartments: the intracellular fluid (ICF) and the extracellular fluid (ECF)
          • The ICF compartment is approximately two thirds of TBW. (MCQ)
          • The ECF compartment represents approximately one third of TBW. (MCQ)
        • ECF is further divided into
          • Blood plasma (blood without cells)
          • Interstitial fluid (ISF) (fluid between cells)
          • Transcellular fluid (synovial intraocular, pericardial, cerebrospinal, and epithelial fluids)
        • Adipose tissue is low in water content
        • obese individuals have a lower fraction of body weight that is water than do normal weight individuals. (MCQ)
        • Substances used to determine the volume of body fluid compartments must have the following characteristics:
          • They must be nontoxic.
          • They must not be synthesized or metabolized in the compartment measured.
          • They must not induce shifts in fluid distribution among different compartments.

 

  • They must be easily and accurately measured.

 

      • Tritiated water and deuterium oxide are used to measure TBW (MCQ)
      • Inulin, mannitol, and sulfate are used to measure ECF. (MCQ)
      • plasma volume can be measured using radioiodinated serum albumin (131I-albumin, or RISA) or Evans blue dye. (MCQ)
      • TBW−ECF = ICF
      • ECF −plasma volume = ISF

 

      • TBW daily turnover due to water intake and loss  (Very High Yield Topic)
        • Water intake averages about 2 L/d, (MCQ)

 

  • Insensible water loss is approximately 0.74 L/d due to water evaporation through the skin and due to respiration. (MCQ)

 

        • Water loss through the skin (0.3–0.4 L/d) is not dependent on sweating and occurs in people born with no sweat glands
        • The rate of water loss is minimized because of the cornified layer of the skin.
        • When this skin layer is lost following severe burns, the rate of water loss increases dramatically to about 3–5 L/d.
        • Water loss due to respiration is about 0.3–0.4 L/d. (MCQ)
        • Water vapor pressure in the lung is approximately 47 mm Hg.

 

  • Inspired air becomes saturated with moisture because it has a lower vapor pressure. In cold weather, vapor pressure in the air decreases even further, enhancing water loss.

 

        • At rest, water loss due to sweating is approximately 0.1 L/d, but this amount increases dramatically during heavy exercise (up to 1–2 L/h).
        • Feces accounts for approximately 0.1–0.2 L/d. (MCQ)
        • Urine accounts for approximately 0.5–1.5 L/d (MCQ)
      • Fluid shifts between compartments follow several basic principles:
        • ICF and ECF are in osmotic equilibrium.
        • Na+ is the major cation of the ECF. (MCQ)

 

  • K+ is the major cationase.

 

    • Equilibration between the ICF and ECF occurs through water movement,

not through movement of osmotically active particles.