( ( The spleen ) ( ( ( ( filters ( ( bacteria and ) ( particulate matter ) ) ) ( -LRB- ( ( especially ( deteriorated ( red ( blood cells ) ) ) ) -RRB- ) ) ) ( from ( the blood ) ) ) . ) )
(ROOT (S (NP (DT The) (NN spleen)) (VP (VBZ filters) (NP (NP (NNS bacteria)) (CC and) (NP (JJ particulate) (NN matter))) (PRN (-LRB- -LRB-) (VP (ADVP (RB especially)) (VBN deteriorated) (NP (JJ red) (NN blood) (NNS cells))) (-RRB- -RRB-)) (PP (IN from) (NP (DT the) (NN blood)))) (. .)))
The spleen filters bacteria and particulate matter (especially deteriorated red blood cells) from the blood.
(ROOT (S (NP (NP (DT The) (JJ main) (NN function)) (PP (IN of) (NP (DT the) (NN spleen)))) (VP (VBZ is) (S (VP (TO to) (VP (VP (VB filter) (NP (DT the) (NN blood))) (CC and) (VP (VB remove) (NP (JJ unwanted) (JJ red) (NN blood) (NNS cells))))))) (. .)))
The main function of the spleen is to filter the blood and remove unwanted red blood cells.