red blood cells osmosis - AS Biology all exams boards and need to know !

so when red blood cells are added to a hypotonic solution , the red blood cell will burst and this is called haemolysis however when they are added to a hypertonic solution they become crenated this means that they become crinkly on the outside edges when water has gone out of the cell by osmosis and this can happen when a person is suffering very bad dehydration and is why drips etc are isotoinc with our blood so this does not happen as the cells can no longer fuction when they have reached this state THIS COMES UP IN MANY EXAM QUESTIONS !