( ( ( ( ( The ( mitral valve ) ) , ) ( so ( ( named ( because ( of ( its resemblance ) ) ) ) ( to ( ( a ( bishop 's ) ) mitre ) ) ) ) ) , ) ( ( is ( ( the ( heart valve ) ) ( that ( ( prevents ( ( the backflow ) ( of ( blood ( from ( the ( left ventricle ) ) ) ) ) ) ) ( into ( ( the ( left atrium ) ) ( of ( the heart ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ mitral) (NN valve)) (, ,) (VP (ADVP (RB so)) (VBN named) (PP (RB because) (IN of) (NP (PRP$ its) (NN resemblance))) (PP (TO to) (NP (NP (DT a) (NN bishop) (POS 's)) (NN mitre)))) (, ,)) (VP (VBZ is) (NP (NP (DT the) (NN heart) (NN valve)) (SBAR (WHNP (WDT that)) (S (VP (VBZ prevents) (NP (NP (DT the) (NN backflow)) (PP (IN of) (NP (NP (NN blood)) (PP (IN from) (NP (DT the) (JJ left) (NN ventricle)))))) (PP (IN into) (NP (NP (DT the) (JJ left) (NN atrium)) (PP (IN of) (NP (DT the) (NN heart)))))))))) (. .)))
The mitral valve, so named because of its resemblance to a bishop's mitre, is the heart valve that prevents the backflow of blood from the left ventricle into the left atrium of the heart.
(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))))))) (. .)))