At this point, {HEAD ~ tapered slits} 2 in {TAIL ~ valve body} 1 close 
in
At this point , { HEAD ~ tapered slits } 2 in { TAIL ~ valve body } 1 close
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH