Therefore, {HEAD ~ needle valves} are used to control {TAIL ~ flow} into delicate human body tissues such as blood vessels, which might be damaged by sudden surges of fluid under pressure 
are used to control
Therefore , { HEAD ~ needle valves } are used to control { TAIL ~ flow } into delicate human body tissues such as blood vessels , which might be damaged by sudden surges of fluid under pressure
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH