The valve is constructed so that {HEAD ~ liquid} can be introduced to or removed from {TAIL ~ the bladder}  
introduced to
The valve is constructed so that { HEAD ~ liquid } can be introduced to or removed from { TAIL ~ the bladder }
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH