( ( ( alveolus ( A ( tiny ( air sac ) ) ) ) ( in ( ( the lungs ) ( ( through which ) ( gases ( are ( ( exchanged ( between ( ( ( the atmosphere ) and ) ( the blood ) ) ) ) ( in respiration ) ) ) ) ) ) ) ) ; )
(ROOT (S (VP (VB alveolus) (NP (DT A) (JJ tiny) (NN air) (NN sac)) (PP (IN in) (NP (NP (DT the) (NNS lungs)) (SBAR (WHPP (IN through) (WHNP (WDT which))) (S (NP (NNS gases)) (VP (VBP are) (VP (VBN exchanged) (PP (IN between) (NP (NP (DT the) (NN atmosphere)) (CC and) (NP (DT the) (NN blood)))) (PP (IN in) (NP (NN respiration)))))))))) (: ;)))
alveolus A tiny air sac in the lungs through which gases are exchanged between the atmosphere and the blood in respiration;
(ROOT (S (NP (NP (DT The) (NNS lungs)) (PP (IN of) (NP (NNS mammals)))) (VP (VBP are) (ADJP (JJ unique) (PP (IN in) (S (VP (VBG having) (NP (NNS alveoli))))))) (. .)))