( ( ( ( Mitral Valve-One ) ( of ( the ( four valves ) ) ) ) ( of ( the heart ) ) ) . )
(ROOT (NP (NP (NNP Mitral) (NNP Valve-One)) (PP (IN of) (NP (DT the) (CD four) (NNS valves))) (PP (IN of) (NP (DT the) (NN heart))) (. .)))
Mitral Valve-One of the four valves of the heart.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD four) (NNS valves)) (PP (IN in) (NP (DT the) (NN heart))))) (. .)))