Osmotic Movement of Fluids and effects on RBC

Osmotic Movement of Fluids and effects on RBC

  • The osmolality of the fluid surrounding cells affects them
    • Isotonic
      • Normal distribution of water and solvent
    • Hypotonic
      • Large amount of water entering the cell
      • Causing the cell to swell
      • Eventually burst
    • Hypertonic
      • Large amount of water leaving the cell
      • Causing it to shrink
      • Eventually crenating

Mechanisms controlling fluid and electrolyte movement

  • To main homeostasis different processes are involved
    • Simple diffusion
      • movement of molecules from an area of high concentration to low concentration
    • Facilitated diffusion
      • Use of a protein carrier in the cell membrane that combine with molecules that are too large to pass easily through the cell membrane, and assists in moving the molecule across the membrane from an area of high to low concentration
    • Active transport.
      • Molecules move against the concentration gradient, but only in the presence of external energy. (sodium-potassium pump)
    • Osmosis
      • Movement of water across a semipermeable membrane from a region of low solute concentration to one of high solute concentration
  • Water is driven by two forces
    • Hydrostatic pressure
      • Blood pressure generated by heart contraction
    • Oncotic pressure
      • Osmotic pressure caused by plasma proteins