hypertonic to man salt water, hypotonic freshwater, isotonic same concentration of blood
the osmosis takes place due to gradient difference and is with reference to the blood of the organsim and is considered hypertonic if it is more concentrated and is termed hypotonic when the surrounding medium is less concentrated when compared to the circulating fluid and isotonic is that the outer medium and the inner circulating medium are of same concentration. It is a relative gradient flow resulting in endosmosis or exosmosis.
