( ( Extensive ( plaque buildup ) ) ( ( is ( ( called ( ( ( atherosclerosis or ) hardening ) ( of ( the arteries ) ) ) ) ( because ( it ( causes ( ( the ( artery walls ) ) ( to ( ( ( thicken and ) lose ) flexibility ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Extensive) (NN plaque) (NN buildup)) (VP (VBZ is) (VP (VBN called) (NP (NP (NNS atherosclerosis) (CC or) (NN hardening)) (PP (IN of) (NP (DT the) (NNS arteries)))) (SBAR (IN because) (S (NP (PRP it)) (VP (VBZ causes) (S (NP (DT the) (NN artery) (NNS walls)) (VP (TO to) (VP (VB thicken) (CC and) (VB lose) (NP (NN flexibility)))))))))) (. .)))
Extensive plaque buildup is called atherosclerosis or hardening of the arteries because it causes the artery walls to thicken and lose flexibility.
(ROOT (S (PP (IN In) (NP (NNS atherosclerosis))) (, ,) (NP (NP (NN thickening)) (PP (IN of) (NP (NP (DT an) (JJ arterial) (NN wall)) (ADJP (JJ due) (PP (TO to) (NP (NN plaque) (NN formation))))))) (VP (MD can) (VP (VB restrict) (NP (NN blood) (NN flow)) (PP (IN through) (NP (DT the) (NN artery))))) (. .)))