Making the cross sectional shape of the channel 46 {HEAD ~ a segment} of a true circle also contributes to {TAIL ~ the functional characteristics} of the valve 
contributes to
Making the cross sectional shape of the channel 46 { HEAD ~ a segment } of a true circle also contributes to { TAIL ~ the functional characteristics } of the valve
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH