( Capillaries ( ( are ( ( those ( small vessels ) ) ( within ( ( the tissues ) ( ( from which ) ( ( oxygen transfer ) ( takes place ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Capillaries)) (VP (VBP are) (NP (NP (DT those) (JJ small) (NNS vessels)) (PP (IN within) (NP (NP (DT the) (NNS tissues)) (SBAR (WHPP (IN from) (WHNP (WDT which))) (S (NP (NN oxygen) (NN transfer)) (VP (VBZ takes) (NP (NN place))))))))) (. .)))
Capillaries are those small vessels within the tissues from which oxygen transfer takes place.
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN transferred) (PP (IN through) (NP (NNS capillaries))))) (. .)))