{HEAD ~ The annular protrusion} further has a distal end with an internal groove with a base portion, {TAIL ~ a front wall} and a rear wall 
has
{ HEAD ~ The annular protrusion } further has a distal end with an internal groove with a base portion , { TAIL ~ a front wall } and a rear wall
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH