( ( The spleen ) ( also ( ( ( ( acts ( like ( a filter ) ) ) , ) ( ( ( collecting and ) removing ) ( ( ( immature or ) ( worn out ) ) ( blood cells ) ) ) ) . ) ) )
(ROOT (S (NP (DT The) (NN spleen)) (ADVP (RB also)) (VP (VBZ acts) (PP (IN like) (NP (DT a) (NN filter))) (, ,) (S (VP (VBG collecting) (CC and) (VBG removing) (NP (ADJP (ADJP (JJ immature)) (CC or) (ADJP (JJ worn) (IN out))) (NN blood) (NNS cells))))) (. .)))
The spleen also acts like a filter, collecting and removing immature or worn out blood cells.
(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.