tissue fluid

• what is tissue fluid?

  the fluid that surrounds tissue cells --> made from substances that leave the blood plasma e.g. oxygen, water and nutrients
• which molecules doesn't tissue fluid contain and why?

  red blood cells

  white blood cells

  plasma proteins

  --> as they are too large to be pushed out the capillary walls
• cells take in oxygen and nutrients from the tissue fluid and release metabolic waste e.g. CO2 into it ---> substances leave by ultrafiltration
• where does tissue fluid leave the capillary and why?

  at the arteriole end

  hydrostatic pressure is high because it comes from the arteries so it is higher than oncotic pressure so fluid is forced out of the capillaries and into the spaces around the cell - forming tissue fluid
• where does tissue fluid reenter the cell and why?

  at the venule end

  hydrostatic pressure decreases as it passes through the capillary because lots of water has left the blood so the hydrostatic pressure is higher in the tissue fluid

  the oncotic pressure is still high because the plasma proteins remain in the blood therefore, oncotic pressure is greater than hydrostatic pressure so water moves back in by osmosis
• what is the effect of plasma proteins?

  they lower the water potential of the blood causing water to move back in by osmosis --> generate the oncotic pressure
• not all of the tissue fluid re-enters the capillaries - some excess tissue fluid is left over. this extra fluid eventually gets returned to the blood through the lymphatic system
• what is the lymphatic system?

  a drainage system made up of lymph vessels
• • the smallest lymph vessels are the lymph capillaries
  • excess tissue fluid passes into the lymph vessels, once inside, it's called lymph
  • valves in the lymph vessels stop the lymph going backwards
  • lymph gradually moves towards the main lymph vessels in the thorax where it's returned to the blood
• which contains red blood cells: blood, tissue fluid or lymph?

  blood

  red blood cells are too big to pass through the capillary walls into the tissue fluid
• which contains white blood cells: blood, tissue fluid or lymph?

  blood and lymph
• which contains platelets: blood, tissue fluid or lymph?

  blood

  platelets are too big to pass through the capillary walls into the tissue fluid
• which contains proteins: blood, tissue fluid or lymph?

  blood

  lymph only contains antibodies
• which contains water blood, tissue fluid or lymph?

  all
• which contains dissolved solutes?

  all