( ( • ( Immovable joints ) ) ( ( ( allow ( no movement ) ) ( because ( ( ( the bones ) ( at ( these joints ) ) ) ( are ( ( held ( securely together ) ) ( by ( dense collagen ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP •) (NNP Immovable) (NNS joints)) (VP (VBP allow) (NP (DT no) (NN movement)) (SBAR (IN because) (S (NP (NP (DT the) (NNS bones)) (PP (IN at) (NP (DT these) (NNS joints)))) (VP (VBP are) (VP (VBN held) (ADVP (RB securely) (RB together)) (PP (IN by) (NP (JJ dense) (NN collagen)))))))) (. .)))
• Immovable joints allow no movement because the bones at these joints are held securely together by  dense collagen.
(ROOT (S (NP (JJ Dense) (NN collagen) (NNS secures)) (ADVP (RB together)) (VP (VP (VBP immovable) (NP (NNS joints))) (CC and) (VP (VBZ prevents) (NP (PRP them)) (PP (IN from) (S (VP (VBG moving)))))) (. .)))