The Bulbourethral Glands
The bulbourethral glands (also known as Cowper’s glands) are a pair of pea shaped exocrine glands located posterolateral to the membranous urethra. They contribute to the final volume of semen by producing a lubricating mucus secretion.
In this article, we shall look at the anatomy of the bulbourethral glands – their structure, vasculature and innervation.
Anatomical Position and Structure
On dissection, the bulbourethral glands can be found in the deep perineal pouch of the male. They are situated posterolaterally to the membranous urethra and superiorly to the bulb of the penis.
The ducts of the gland penetrate the perineal membrane alongside the membranous urethra and open into the proximal portion of the spongy urethra.
The glands themselves can be described as compound tubulo-alveolar glands lined by columnar epithelium.
Embryologically the bulbourethral glands are derived from the urogenital sinus, along with the bladder, prostate and urethra. Their development is greatly influenced by DHT (dihydrotestosterone).
During sexual arousal, the bulbourethral glands produce a mucus secretion containing glycoproteins. This substance has three main purposes:
- Serves as lubrication medium for the urethra and the tip of the penis.
- Expels any residue of urine, dead cells or mucous through the urethral meatus, preparing a clean and lubricated pathway for ejaculation.
- Helps to neutralise residual acidity in the male urethra (secretions are alkaline).
It is apparent that normally these secretions are devoid of any spermatozoa, as ejaculation occurs further down at the prostatic urethra level. However, occasionally these secretions (also known as pre-ejaculate) may carry spermatozoa that remain in the urethra after a previous ejaculation (keep in mind that spermatozoa in body temperature survive for more than 48 hours!).
This may be obviated by urination and thus washing out the urethra. However, although rare, it may represent a cause of unintended pregnancy during unprotected sexual intercourse
The arterial supply of the bulbourethral glands is derived from the arteries to the bulb of the penis.
In a mammal study (in pigs), neurons projecting to the bulbourethral glands were found in pelvic ganglia (PG), sympathetic chain ganglia (L2–S3), the caudal mesenteric ganglion and dorsal root ganglia (L1–L3, S1–S3);
They reach the bulbourethral glands via the the hypogastric nerve and the pelvic nerve or pelvic branch of the pudendal nerve.
Like the seminal vesicles the bulbourethral glands drain into the internal and external iliac lymph nodes