( Excretion ( ( ( ( is chiefly ) ( by ( the kidneys ) ) ) ( through ( ( ( glomerular filtration ) and ) ( tubular secretion ) ) ) ) . ) )
(ROOT (S (NP (NNP Excretion)) (VP (VBZ is) (ADVP (RB chiefly)) (PP (IN by) (NP (DT the) (NNS kidneys))) (PP (IN through) (NP (NP (NN glomerular) (NN filtration)) (CC and) (NP (JJ tubular) (NN secretion))))) (. .)))
Excretion is chiefly by the kidneys through glomerular filtration and tubular secretion.
(ROOT (S (NP (NP (DT The) (JJ main) (NNS functions)) (PP (IN of) (NP (NN epithelia)))) (VP (VBP are) (NP (NP (NN protection)) (PP (IN from) (NP (NP (DT the) (NN environment) (, ,) (NN coverage) (, ,) (NN secretion) (CC and) (NN excretion)) (, ,) (NP (NN absorption)) (, ,) (CC and) (NP (NN filtration)))))) (. .)))