( ( As ( the ( man ejaculates ) ) ) ( , ( sperm ( ( combines ( ( ( with ( ( fluid ( from ( the seminal ) ) ) vesicles ) ) and ) ( with ( ( ( a ( thick secretion ) ) ( from ( the ( prostate gland ) ) ) ) ( thus ( causing semen ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN As) (NP (DT the) (NN man) (NNS ejaculates))) (, ,) (NP (NN sperm)) (VP (VBZ combines) (PP (PP (IN with) (NP (ADJP (JJ fluid) (PP (IN from) (NP (DT the) (NN seminal)))) (NNS vesicles))) (CC and) (PP (IN with) (S (NP (NP (DT a) (JJ thick) (NN secretion)) (PP (IN from) (NP (DT the) (NN prostate) (NN gland)))) (ADVP (RB thus)) (VP (VBG causing) (NP (NN semen))))))) (. .)))
As the man ejaculates, sperm combines with fluid from the seminal vesicles and with a thick secretion from the prostate gland thus causing semen.
(ROOT (S (NP (DT The) (NN prostate) (NN gland)) (VP (VBZ secretes) (NP (NP (DT a) (NN fluid)) (SBAR (WHNP (WDT that)) (S (VP (VBZ mixes) (PP (IN with) (NP (NN sperm))) (S (VP (TO to) (VP (VB help) (NP (NN form) (NN semen)))))))))) (. .)))