( ( A venule ) ( ( is ( ( a ( ( very small ) ( blood vessel ) ) ) ( in ( ( the microcirculation ) ( that ( ( allows blood ) ( to ( ( return ( from ( the ( capillary beds ) ) ) ) ( to ( drain ( into ( ( ( the ( larger ( blood vessels ) ) ) , ) ( the veins ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN venule)) (VP (VBZ is) (NP (NP (DT a) (ADJP (RB very) (JJ small)) (NN blood) (NN vessel)) (PP (IN in) (NP (NP (DT the) (NN microcirculation)) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (NP (NN blood)) (S (VP (TO to) (VP (VB return) (PP (IN from) (NP (DT the) (JJ capillary) (NNS beds))) (S (VP (TO to) (VP (VB drain) (PP (IN into) (NP (NP (DT the) (JJR larger) (NN blood) (NNS vessels)) (, ,) (NP (DT the) (NNS veins))))))))))))))))) (. .)))
A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins.
(ROOT (S (NP (NNS Capillaries)) (VP (VBP are) (NP (NP (DT the) (JJS smallest) (NN type)) (PP (IN of) (NP (NN blood) (NNS vessels))))) (. .)))