( ( At ( ( the point ) ( where ( ( each ( of ( the capillaries ) ) ) ( originates ( from ( an arteriole ) ) ) ) ) ) ) ( , ( ( a ( smooth ( muscle fiber ) ) ) ( ( encircles ( the capillary ) ) . ) ) ) )
(ROOT (S (PP (IN At) (NP (NP (DT the) (NN point)) (SBAR (WHADVP (WRB where)) (S (NP (NP (DT each)) (PP (IN of) (NP (DT the) (NNS capillaries)))) (VP (VBZ originates) (PP (IN from) (NP (DT an) (NN arteriole)))))))) (, ,) (NP (DT a) (JJ smooth) (NN muscle) (NN fiber)) (VP (VBZ encircles) (NP (DT the) (NN capillary))) (. .)))
At the point where each of the capillaries originates from an arteriole, a smooth muscle fiber encircles the capillary.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT the) (JJ smooth) (NN muscle)) (VP (VBZ relaxes)))) (, ,) (NP (DT the) (NNS arterioles)) (VP (VBD dilate) (, ,) (S (VP (VBG allowing) (NP (NN blood)) (S (VP (TO to) (VP (VB enter) (NP (DT the) (NNS capillaries)))))))) (. .)))