( ( The heart ) ( ( ( ( becomes ( ( the ( first ( working organ ) ) ) ( in ( the ( human body ) ) ) ) ) , ) ( ( ( pumping ( by ( rhythmically opening ) ) ) and ) ( squeezing ( shut ( ( just ( 17 days ) ) ( after conception ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN heart)) (VP (VBZ becomes) (NP (NP (DT the) (JJ first) (JJ working) (NN organ)) (PP (IN in) (NP (DT the) (JJ human) (NN body)))) (, ,) (S (VP (VP (VBG pumping) (PP (IN by) (NP (JJ rhythmically) (NN opening)))) (CC and) (VP (VBG squeezing) (S (VP (VBN shut) (PP (NP (RB just) (CD 17) (NNS days)) (IN after) (NP (NN conception))))))))) (. .)))
The heart becomes the first working organ in the human body, pumping by rhythmically opening and squeezing shut just 17 days after conception.
(ROOT (S (PP (IN In) (NP (NNS humans))) (, ,) (NP (DT the) (NN heart)) (VP (VBZ is) (NP (DT the) (JJ first) (NN organ) (S (VP (TO to) (VP (VP (VB form)) (CC and) (VP (VB become) (ADJP (JJ functional)))))))) (. .)))