Food enters through the mouth, where teeth perform the
initial breakdown of food into smaller particles and mix it with saliva. The
food passes down the pharynx situated behind the mouth and nose, down into the
oesophagus, into the, stomach where further breakdown of food occurs, into the small intestine and
finally into the large intestine.
Selective permeable means it selects what goes out and comes into the cell. If the cell membrane wasnt selective then things could enter the cell and destroy it.
