( ( Blood ( rich ( in oxygen ) ) ) ( ( ( ( ( leaves ( the lungs ) ) ( through ( the ( pulmonary vein ) ) ) ) and ) ( enters ( the ( left atrium ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Blood)) (ADJP (JJ rich) (PP (IN in) (NP (NN oxygen))))) (VP (VP (VBZ leaves) (NP (DT the) (NNS lungs)) (PP (IN through) (NP (DT the) (JJ pulmonary) (NN vein)))) (CC and) (VP (VBZ enters) (NP (DT the) (JJ left) (NN atrium)))) (. .)))
Blood rich in oxygen leaves the lungs through the pulmonary vein and enters the left atrium.
(ROOT (S (NP (NP (NNP Blood)) (PP (IN from) (NP (DT the) (NNS lungs)))) (VP (VBZ enters) (PP (IN into) (NP (DT the) (JJ left) (NN atrium)))) (. .)))