( ( ( ( The ( shaded areas ) ) and ) ( heavy arrows ) ) ( represent ( ( the rate ) ( of ( ( absorption ( of ( the solute ) ) ) ( -LRB- ( ( ( that ( ( is , ) ( ( the difference ) ( between ( filtration ( rate ( and ( excretion rate ) ) ) ) ) ) ) ) . ) -RRB- ) ) ) ) ) ) )
(ROOT (S (NP (NP (DT The) (JJ shaded) (NNS areas)) (CC and) (NP (JJ heavy) (NNS arrows))) (VP (VBP represent) (NP (NP (DT the) (NN rate)) (PP (IN of) (NP (NP (NN absorption)) (PP (IN of) (NP (DT the) (NN solute))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (, ,) (NP (NP (DT the) (NN difference)) (PP (IN between) (NP (JJ filtration) (NN rate) (CC and) (NN excretion) (NN rate)))))) (. .)) (-RRB- -RRB-))))))))
The shaded areas and heavy arrows represent the rate of absorption of the solute (that is, the difference between filtration rate and excretion rate.)
(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)))))) (. .)))