( ( ( ( ( ( ( The thrust ) ( of ( the ( anterior extremities ) ) ) ) ( carries forward ) ) and ) upward ) ( ( ( the body ) ( of ( ( ( the sternum ) , ) ( which ( moves ( on ( ( ( ( the joint ) ( between it ) ) and ) ( ( ( ( ( the manubrium ) , ) and ) thus ) ( the ( antero-posterior ( thoracic diameter ) ) ) ) ) ) ) ) ) ) ) ( is increased ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (NN thrust)) (PP (IN of) (NP (DT the) (NN anterior) (NNS extremities)))) (VP (VBZ carries) (ADVP (RB forward)))) (CC and) (ADVP (RB upward)) (S (NP (NP (DT the) (NN body)) (PP (IN of) (NP (NP (DT the) (NN sternum)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ moves) (PP (IN on) (NP (NP (NP (DT the) (NN joint)) (PP (IN between) (NP (PRP it)))) (CC and) (NP (NP (DT the) (NN manubrium)) (, ,) (CC and) (ADVP (RB thus)) (NP (DT the) (JJ antero-posterior) (JJ thoracic) (NN diameter))))))))))) (VP (VBZ is) (VP (VBN increased)))) (. .)))
The thrust of the  anterior extremities carries forward and upward the body of the sternum, which moves on the joint between it and the manubrium, and thus the antero-posterior thoracic diameter is increased.
(ROOT (S (NP (DT The) (NN sternum)) (VP (VBZ is) (NP (NP (DT the) (NN name)) (PP (IN of) (NP (NP (DT the) (JJ elongated) (NN bony) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ anchors) (NP (DT the) (JJ anterior) (JJ thoracic) (NN cage))))))))) (. .)))