{HEAD ~ The anchor structures} may take {TAIL ~ many forms}, and may include barbed, helical, and crimp type anchors 
take
{ HEAD ~ The anchor structures } may take { TAIL ~ many forms } , and may include barbed , helical , and crimp type anchors
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH