( ( The ( white reaction ) ) ( ( ( ( is ( due ( to ( ( ( ( constriction ( of ( precapillary sphincters ) ) ) , ) possibly ) ( combined ( with ( changes ( in ( the ( endothelial cells ) ) ) ) ) ) ) ) ) ) , ) ( so ( that ( ( red ( blood cells ) ) ( ( do not ) ( flow ( through ( the capillaries ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ white) (NN reaction)) (VP (VBZ is) (ADJP (JJ due) (S (VP (TO to) (VP (VB constriction) (PP (IN of) (NP (JJ precapillary) (NNS sphincters))) (, ,) (ADVP (RB possibly)) (PP (VBN combined) (PP (IN with) (NP (NP (NNS changes)) (PP (IN in) (NP (DT the) (JJ endothelial) (NNS cells)))))))))) (, ,) (SBAR (RB so) (IN that) (S (NP (JJ red) (NN blood) (NNS cells)) (VP (VBP do) (RB not) (VP (VB flow) (PP (IN through) (NP (DT the) (NNS capillaries)))))))) (. .)))
The white reaction is due to constriction of precapillary sphincters, possibly combined with changes in the endothelial cells, so that red blood cells do not flow through the capillaries.
(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)))))) (. .)))