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