The funnel shaped occlusion balloon seals the walls of {HEAD ~ the vessel} to establish {TAIL ~ retrograde flow} of blood 
The funnel shaped occlusion balloon seals the walls of { HEAD ~ the vessel } to establish { TAIL ~ retrograde flow } of blood
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH