( Digestion ( ( ( ( ( begins ( in ( ( ( the mouth ) , ) ( when ( we ( ( chew and ) swallow ) ) ) ) ) ) , ) and ) ( is ( completed ( in ( the ( small intestine ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Digestion)) (VP (VP (VBZ begins) (PP (IN in) (NP (NP (DT the) (NN mouth)) (, ,) (SBAR (WHADVP (WRB when)) (S (NP (PRP we)) (VP (VB chew) (CC and) (VB swallow))))))) (, ,) (CC and) (VP (VBZ is) (VP (VBN completed) (PP (IN in) (NP (DT the) (JJ small) (NN intestine)))))) (. .)))
Digestion begins in the mouth, when we chew and swallow, and is completed in the small intestine.
(ROOT (S (NP (NNP Digestion)) (VP (VBZ begins) (PP (IN in) (NP (DT the) (NN mouth)))) (. .)))