( ( ( ( ( They ( help ( to ( ( move cells ) around ) ) ) ) , ) but ) ( they ( ( are also ) ( present ( on ( ( the ( outer surface ) ) ( of ( some ( epithelial tissues ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP They)) (VP (VBP help) (S (VP (TO to) (VP (VB move) (NP (NNS cells)) (ADVP (RB around))))))) (, ,) (CC but) (S (NP (PRP they)) (VP (VBP are) (ADVP (RB also)) (ADJP (JJ present) (PP (IN on) (NP (NP (DT the) (JJ outer) (NN surface)) (PP (IN of) (NP (DT some) (JJ epithelial) (NNS tissues)))))))) (. .)))
They help to move cells around, but they are also present on the outer surface of some epithelial tissues.
(ROOT (S (NP (NNP Epithelial) (. ?) (NNP tissue)) (VP (VBZ consists) (PP (IN of) (NP (NP (NNS cells)) (SBAR (WHNP (WHNP (WDT that) (NN cover)) (NP (JJ inner) (CC and) (JJ outer) (NN body))) (S (VP (VBZ surfaces))))))) (. .)))