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