How are elements like iron recognized and routed to the right places for use in the body?
A wikipedia source gives you general informations and precise details about the locations and methods of absorption and distribution. Reading the page is well recommended, I will add the quote to save others time:

en.wikipedia.org/wiki/Human_iron_metabolism#Dietary_iron_uptake :


  Like most mineral nutrients, the majority of the iron absorbed from
  digested food or supplements is absorbed in the duodenum by
  enterocytes of the duodenal lining. These cells have special molecules
  that allow them to move iron into the body. To be absorbed, dietary
  iron can be absorbed as part of a protein such as heme protein or iron
  must be in its ferrous Fe2+ form. 
  
  A ferric reductase enzyme on the enterocytes’ brush border, duodenal
  cytochrome B (Dcytb), reduces ferric Fe3+ to Fe2+.[9] 
  
  A protein called divalent metal transporter 1 (DMT1), which can
  transport several divalent metals across the plasma membrane, then
  transports iron across the enterocyte’s cell membrane into the cell.
  
  These intestinal lining cells can then either store the iron as
  ferritin, which is accomplished by Fe3+ binding to apoferritin (in
  which case the iron will leave the body when the cell dies and is
  sloughed off into feces), or the cell can release it into the body via
  the only known iron exporter in mammals, ferroportin. 
  
  Hephaestin, a ferroxidase that can oxidize Fe2+ to Fe3+ and is found
  mainly in the small intestine, helps ferroportin transfer iron across
  the basolateral end of the intestine cells. In contrast, ferroportin
  is post-translationally repressed by hepcidin, a 25-amino acid peptide
  hormone. 
  
  The body regulates iron levels by regulating each of these steps. For
  instance, enterocytes synthesize more Dcytb, DMT1 and ferroportin in
  response to iron deficiency anemia.[10] Iron absorption from diet is
  enhanced in the presence of vitamin C and diminished by excess
  calcium, zinc, or manganese.