( ( ( ( ( The duodenum ) ( is ( ( the ( first part ) ) ( of ( the ( small intestine ) ) ) ) ) ) and ) ( ( most ( of ( the ( chemical digestion ) ) ) ) ( occurs here ) ) ) . )
(ROOT (S (S (NP (DT The) (NN duodenum)) (VP (VBZ is) (NP (NP (DT the) (JJ first) (NN part)) (PP (IN of) (NP (DT the) (JJ small) (NN intestine)))))) (CC and) (S (NP (NP (JJS most)) (PP (IN of) (NP (DT the) (NN chemical) (NN digestion)))) (VP (VBZ occurs) (ADVP (RB here)))) (. .)))
The duodenum is the first part of the small intestine and most of the chemical digestion occurs here.
(ROOT (S (PP (IN In) (NP (DT the) (NN body))) (, ,) (NP (NN chemical) (NN digestion)) (ADVP (RB mainly)) (VP (VBZ takes) (NP (NP (NN place)) (PP (IN in) (NP (DT the) (JJ small) (NN intestine))))) (. .)))
In the body, chemical digestion mainly takes place in the small intestine.