( ( Mitral valve ) ( ( is ( one ( of ( ( the valves ) ( of ( ( ( the heart ) , ) ( ( whose function ) ( is ( ( ( ( to ( keep ( ( the blood ) ( ( flowing ( in ( one direction ) ) ) ( through ( ( the ( left side ) ) ( of ( the heart ) ) ) ) ) ) ) ) , ) and ) ( to ( ( prevent ( backflow ( of blood ) ) ) ( when ( ( the heart ) contracts ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Mitral) (NN valve)) (VP (VBZ is) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (NNS valves)) (PP (IN of) (NP (NP (DT the) (NN heart)) (, ,) (SBAR (WHNP (WP$ whose) (NN function)) (S (VP (VBZ is) (S (VP (VP (TO to) (VP (VB keep) (NP (NP (DT the) (NN blood)) (VP (VBG flowing) (PP (IN in) (NP (CD one) (NN direction))) (PP (IN through) (NP (NP (DT the) (JJ left) (NN side)) (PP (IN of) (NP (DT the) (NN heart))))))))) (, ,) (CC and) (VP (TO to) (VP (VB prevent) (NP (NP (NN backflow)) (PP (IN of) (NP (NN blood)))) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN heart)) (VP (VBZ contracts))))))))))))))))) (. .)))
Mitral valve is one of the valves of the heart, whose function is to keep the blood flowing in one direction through the left side of the heart, and to prevent backflow of blood when the heart contracts.
(ROOT (S (NP (NNP Heart) (NNS valves)) (VP (VBP prevent) (NP (NP (DT the) (NN backflow)) (PP (IN of) (NP (NN blood)))) (PP (IN from) (S (VP (VBG happening) (PP (IN in) (NP (DT the) (NN heart))))))) (. .)))