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