Tissue and Lymph Fluid

Cards (23)

  • Tissue fluid
    Fluid that passes out of the blood and bathes the tissue cells
  • Formation of tissue fluid
    1. Fluid passes out of the blood at the arterial end of the capillary
    2. Fluid returns to the blood at the venous end of the capillary
  • Hydrostatic pressure

    The pressure exerted by the blood at the arterial end of the capillary
  • Osmotic pressure
    The tendency for water to move back into the blood by osmosis due to the plasma proteins
  • At the arterial end of the capillary

    Hydrostatic pressure is greater than osmotic pressure, causing tissue fluid to form
  • At the venous end of the capillary

    Hydrostatic pressure is less than osmotic pressure, causing water to move back into the blood
  • Around 90% of tissue fluid is reabsorbed back into the blood
  • Lymph fluid
    The remaining 10% of tissue fluid that drains into lymph capillaries and vessels
  • Movement of lymph fluid
    1. Lymph vessels are squeezed by nearby skeletal muscles
    2. Valves in lymph vessels help keep lymph fluid moving forward
    3. Lymph fluid eventually returns to the bloodstream under the collar bone
  • The lymphatic system also plays a role in immunity
  • Tissue fluid
    Liquid that passes between the capillaries and the cells of the tissues
  • Capillary walls
    • Single layer of epithelial cells
    • Act as a selectively permeable membrane
    • Allow water and solutes of low RMM to pass through
    • Proteins remain in the capillaries
  • Formation of tissue fluid
    1. Ultrafiltration
    2. Combination of blood pressure forcing materials out of capillaries and osmotic pressure pulling materials into capillaries
  • Composition of tissue fluid
    • Water
    • Glucose
    • Amino acids
    • Fatty acids
    • Glycerol
    • Mineral salts
    • Dissolved gases
    • Vitamins
  • Composition of plasma
    • Red blood cells
    • White blood cells
    • Platelets
    • Large plasma proteins
  • Tissue fluid movement at start of capillary bed
    1. Water and small solutes pass out through capillary endothelium
    2. Hydrostatic pressure due to blood pressure is greater than osmotic pressure due to proteins
  • Tissue fluid movement at end of capillary bed
    1. Water and solutes flow back into capillaries
    2. Hydrostatic pressure has dropped and osmotic pressure causes water and solutes to flow back in
  • About 99% of the fluid that leaves the blood at the arterial end of the capillary bed returns at the venous end
  • The rest of the tissue fluid returns via the lymphatic system
  • Edema
    Fluid accumulation around the tissues (swelling)
  • Causes of edema
    • Excessively high blood pressure
    • Protein deficient diet (kwashiorkor)
    • Low protein levels in the blood caused by malnutrition, kidney and liver disease
  • Components of the lymphatic system

    • Lymph vessels
    • Lymph nodes
    • Thymus
    • Spleen
    • Bone marrow
  • Lymph is returned to the bloodstream via the right subclavian vein