a housing having a passage sized to receive {HEAD ~ a catheter} having {TAIL ~ an outer wall} 
having
a housing having a passage sized to receive { HEAD ~ a catheter } having { TAIL ~ an outer wall }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL