The major contribution to the semen from:
Semen which is ejaculated during male sexual act is composed of fluid and sperm.

vasdeferens-10%
seminal vesicles-60%-mucoid consistency
prostate gland-30%-milky
so the bulk of semen is seminal vesicle fluid
Testes
Seminal vesicles
Prostate
Bulbourethral and urethral glands