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• Blood plasma


  The liquid component of blood, separated from the blood cells by centrifugation
• Centrifugation of blood


  Denser substances sink, less dense substances rise to the top
• Components of blood after centrifugation


  • Red blood cells (45-44%)
  • Platelets (1%)
  • Plasma (55%)
• Plasma


  • Mostly water, also contains ions, proteins, nutrients, waste, gases
  • Water is an important component as it is a good solvent and has high specific heat capacity
• Tissue fluid (interstitial fluid)

  Fluid that bathes the cells outside the blood vessels, acts as medium for exchange of materials between cells and blood
• Tissue fluid is formed from

  Blood plasma
• Formation of tissue fluid


  1. Difference in blood pressure between arterial and venous ends of capillaries

  2. Plasma forced out of capillaries through endothelial pores
• Composition of tissue fluid

  • Contains water, gases, glucose, fatty acids, ions
  • Contains smaller proteins like antibodies, but no large proteins
  • Contains some white blood cells, but no red blood cells or platelets
  • Has lower oxygen concentration than blood plasma
• Return of tissue fluid to blood


  1. Hydrostatic pressure gradient at arterial end pushes fluid out

  2. Solute concentration gradient at venous end draws fluid back in

  3. 90% of tissue fluid returns to blood, 10% enters lymphatic system
• Lymph drains into subclavian veins near the heart
• Comparison of blood plasma, tissue fluid, and lymph


  • Blood plasma
  • Tissue fluid
  • Lymph
• Lymph is not in the syllabus, this is extra information