( ( The ( ( most frequent ) ( anatomic substrate ) ) ) ( ( is ( ( ( precapillary or ) capillary ) ( pulmonary ( vascular dilatation ) ) ) ) . ) )
(ROOT (S (NP (DT The) (ADJP (RBS most) (JJ frequent)) (JJ anatomic) (NN substrate)) (VP (VBZ is) (NP (ADJP (JJ precapillary) (CC or) (JJ capillary)) (JJ pulmonary) (NN vascular) (NN dilatation))) (. .)))
The most frequent anatomic substrate is precapillary or capillary pulmonary vascular dilatation.
(ROOT (NP (NP (NP (DT The) (ADJP (RB precapillary) (JJ sphincters)) (NN regulate)) (PRN (-LRB- -LRB-) (PRP s) (-RRB- -RRB-))) (NP (NP (DT the) (NN passage)) (PP (IN of) (NP (NP (NN blood)) (PP (IN into) (NP (JJ capillary) (NNS beds)))))) (. .)))