The outer peripheral cell wall includes {HEAD ~ an outermost peripheral cell wall} forming part of {TAIL ~ the outer peripheral surface} of the block 
The outer peripheral cell wall includes { HEAD ~ an outermost peripheral cell wall } forming part of { TAIL ~ the outer peripheral surface } of the block
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH