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