( ( The ( right atrium ) ) ( ( ( ( ( receives ( blood return ) ) ( from ( ( ( the body ) ( -LRB- ( systemic -RRB- ) ) ) ( under ( low pressure ) ) ) ) ) , ) ( ( ( pumps ( the blood ) ) ( into ( the ( right ventricle ) ) ) ) ( under ( ( low pressure ) ( which ( then ( ( ( pumps blood ) ( under ( ( slightly higher ) pressure ) ) ) ( to ( the lungs ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ right) (NN atrium)) (VP (VBZ receives) (NP (NN blood) (NN return)) (PP (IN from) (NP (NP (NP (DT the) (NN body)) (PRN (-LRB- -LRB-) (NP (NNP systemic)) (-RRB- -RRB-))) (PP (IN under) (NP (JJ low) (NN pressure))))) (, ,) (S (VP (VBG pumps) (NP (DT the) (NN blood)) (PP (IN into) (NP (DT the) (JJ right) (NN ventricle))) (PP (IN under) (NP (NP (JJ low) (NN pressure)) (SBAR (WHNP (WDT which)) (S (ADVP (RB then)) (VP (VBD pumps) (NP (NN blood)) (PP (IN under) (NP (ADJP (RB slightly) (JJR higher)) (NN pressure))) (PP (TO to) (NP (DT the) (NNS lungs))))))))))) (. .)))
The right atrium receives blood return from the body ( systemic ) under low pressure, pumps the blood into the right ventricle under low pressure which then pumps blood under slightly higher pressure to the lungs.
(ROOT (S (NP (NP (DT The) (JJ right) (NN atrium)) (PP (IN of) (NP (DT the) (NN heart)))) (VP (VBZ receives) (SBAR (S (NP (DT the) (NN blood)) (VP (VBZ is) (VP (VBN pumped) (PP (IN from) (NP (NP (NNS veins)) (PP (IN of) (NP (DT the) (JJ systemic) (NN circuit)))))))))) (. .)))