( ( ( Oxygen delivery ) ( to ( surrounding tissues ) ) ) ( ( ( takes place ) ( through ( ( the ( thin ( , ( porous walls ) ) ) ) ( of ( ( the smallest ) ( of ( ( ( these ( interconnecting vessels ) ) , ) ( known ( as ( ( capillaries , ) ( where ( ( the blood ) ( flows ( most slowly ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NN Oxygen) (NN delivery)) (PP (TO to) (NP (VBG surrounding) (NNS tissues)))) (VP (VBZ takes) (NP (NN place)) (PP (IN through) (NP (NP (DT the) (JJ thin) (, ,) (JJ porous) (NNS walls)) (PP (IN of) (NP (NP (DT the) (JJS smallest)) (PP (IN of) (NP (NP (DT these) (VBG interconnecting) (NNS vessels)) (, ,) (VP (VBN known) (PP (IN as) (NP (NP (NNS capillaries)) (, ,) (SBAR (WHADVP (WRB where)) (S (NP (DT the) (NN blood)) (VP (VBZ flows) (ADVP (RBS most) (RB slowly))))))))))))))) (. .)))
Oxygen delivery to surrounding tissues takes place through the thin, porous walls of the smallest of these interconnecting vessels, known as capillaries , where the blood flows most slowly.
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN transferred) (PP (IN through) (NP (NNS capillaries))))) (. .)))