The valves regulate {HEAD ~ fluid flow} to {TAIL ~ the second chamber} in accordance with electrical signals from the heart 
The valves regulate { HEAD ~ fluid flow } to { TAIL ~ the second chamber } in accordance with electrical signals from the heart
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH