Bulbourethral glands also called Cowper glands are two small structures (pea-sized) that secretes lubricating mucus into the urethra during sexual arousal.
Each of the glands provide a fluid medium for the sperm (contribute mucus-containing fluid to semen).
These glands lie on either side of the urethra, at the base of the penis.
Reference: http://www.phoenix5.org/glossary/graphics/malereprourin.jpg
