The bladder has an annular form and {HEAD ~ a pair} of {TAIL ~ opening} extending through the bladder in the axial direction of the bladder 
of
The bladder has an annular form and { HEAD ~ a pair } of { TAIL ~ opening } extending through the bladder in the axial direction of the bladder
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH