( ( The ( mitral valve ) ) ( ( is ( one ( of ( ( the ( heart 's ) ) ( four valves ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ mitral) (NN valve)) (VP (VBZ is) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (NN heart) (POS 's)) (CD four) (NNS valves))))) (. .)))
The mitral valve is one of the heart's four valves.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD four) (NNS valves)) (PP (IN in) (NP (DT the) (NN heart))))) (. .)))