( ( One ( of ( ( the ( major functions ) ) ( of ( the spleen ) ) ) ) ) ( ( is ( to ( ( remove ( ( old and ) worn ) ) ( out ( red ( blood cells ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (CD One)) (PP (IN of) (NP (NP (DT the) (JJ major) (NNS functions)) (PP (IN of) (NP (DT the) (NN spleen)))))) (VP (VBZ is) (S (VP (TO to) (VP (VB remove) (ADJP (JJ old) (CC and) (JJ worn)) (PP (IN out) (NP (JJ red) (NN blood) (NNS cells))))))) (. .)))
One of the major functions of the spleen is to remove old and worn out red 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.