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