tissue fluid

• explain role of heart in formation of tissue fluid (2)

  • contraction of ventricles produces high hydrostatic pressure
  • forces water out of capillaries
• lymphoedema is a swelling in legs which may be caused by blockage in lymphatic system. suggest how a blockage in lymphatic system could cause lymphodema (1)

  • excess tissue fluid canot be reabsorbed
• use info in figure to explain how tissue fluid is formed (2)

  • outward pressure of 3.2
  • forces small molecules out of capillary

  
• the hydrostatic pressure falls from the arteriole end of capillary to venule end of capillay. explain why (1)

  • loss of water
• high blood pressure leads to an accumulation of tissue fluid. explain how (3)

  • high bp = high hydrostatic pressure
  • increases outward pressure from arterial end of capillary
  • so more tissue fluid is formed
• the water potential of blood plasma is more negative at venule end of capillary than at ateriole end. explain why (3)

  • water had left the capillary
  • proteins too large to leave capillary
  • increasing concentration of blood proteins
• some people produce much higher ventricular blood pressure than normal. this can cause tissue fluid to build up outside the blood capillaries of these people. explain why (2)

  • more fluid forced out of capillary
  • lymphatic system cannot drain away all excess fluid
• a capillary has a thin wall. this leads to rapid exchange of substances between the body & tissue fluid. explain why (1)

  • short diffusion pathway
• Kwashiorkor is a disease caused by a lack of protein in the blood. this leads to a swollen abdomen due to a build up of tissue fluid. explain why a lack of protein in the blood causes a build up of tissue fluid (3)

  • water potential is higher/less negative
  • less water removed
  • by osmosis
• high absorption of salt from the diet can result in a higher than normal concentration of salt in the blood plasma entering capillaries. this can lead to a build-up of tissue fluid. explain how (2)

  • results in lower water potential of tissue fluid
  • so less water returns to capillary by osmosis
• describe how tissue fluid is formed & how it is returned to circulatory system (6)

  • high hydrostatic pressure
  • forces water out
  • large proteins remain in capillary
  • low water potential in capillary
  • due to proteins
  • water enters capillary
  • by osmosis
• the diagram shows part of a capillary & some cells surrounding it. name fluid X & Y (2)

  • x - plasma
  • y - tissue fluid

  
• describe & explain one way in which composition of fluid Y differs from X (2)

  • fluid Y contains no proteins as molecules are too large to pass through capillary wall

  
• explain how fluid leaves capillary at aterial end (2)

  • hydrostatic pressure
  • greater than osmotic effect which forces molecules out
• in humans substances move out of the capillaries to form tissue fluid. describe how this tissue fluid is returned to the circulatory system? (3)

  hydrostatic pressure lower in capillary

  water returns

  by osmosis

  water potential lower in blood