The final addition to semen is made by two bulbourethral glands that release a thick, salty fluid that lubricates the end of the urethra and the vagina, and helps to clean urine residues from the penile urethra. The fluid from these accessory glands is released after the male becomes sexually aroused, and shortly before the release of the semen. It is therefore sometimes called pre-ejaculate. It is important to note that, in addition to the lubricating proteins, it is possible for bulbourethral fluid to pick up sperm already present in the urethra, and therefore it may be able to cause pregnancy (Pic. 1).

Anatomical structure

Bulbourethral glands (Cowper’s glands) are located posterior and lateral to the membranous portion of the urethra at the base of the penis, between the two layers of the fascia of the urogenital diaphragm, in the deep perineal pouch (Pic. 2). They are enclosed by transverse fibers of the sphincter urethrae membranaceae muscle.

Histological structure

They are composed of several lobules held together by a fibrous covering. Each lobule consists of a number of acini, lined by columnar epithelial cells (Pic. 3), opening into a duct that joins with the ducts of other lobules to form a single excretory duct. This duct is approximately 2.5 cm long and opens into the bulbar urethra at the base of the penis. The glands gradually diminish in size with advancing age.

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Anatomy of the Male Reproductive System ―sourced from Lumen licensed under CC BY 4.0
Bulbourethral gland ―sourced from Wikipedia licensed under CC BY-SA 3.0
Prostatic urethra ―by Mcstrother licensed under CC BY 3.0
Illu penis ―by unknown licensed under CC0 1.0
Bulbourethral gland -- very high mag ―by Nephron licensed under CC BY-SA 3.0
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