Prostatic Urethra

1. Overview

The prostatic urethra is the first and widest portion of the male urethra, passing through the prostate gland. It serves as a common pathway for urine from the bladder and for seminal fluid during ejaculation. It is surrounded entirely by the prostate and plays an important role in the coordinated function of the urinary and reproductive systems in males.

2. Location

The prostatic urethra begins at the internal urethral orifice at the base of the urinary bladder and passes through the prostate gland, ending where it transitions into the membranous urethra. Key anatomical landmarks include:

• Superiorly: Continuous with the bladder neck.

• Inferiorly: Continues as the membranous urethra after exiting the prostate apex.

• Anteriorly: Related to the pubic symphysis (separated by the retropubic space).

• Posteriorly: Adjacent to the rectum (important during digital rectal examination).

3. Structure

The prostatic urethra measures about 3 cm in length and has several notable internal and external features:

Internal Features:

• Urethral crest: A longitudinal ridge along the posterior wall of the prostatic urethra.

• Seminal colliculus (verumontanum): A rounded elevation on the urethral crest containing several important openings:

  • Prostatic utricle: A small blind pouch, embryologically derived from the Müllerian duct.

  • Openings of the ejaculatory ducts: Deliver semen from the vas deferens and seminal vesicles.

• Prostatic ducts: Numerous small openings along the sides of the urethral crest that allow prostatic secretions to enter the urethra.

Wall Composition:

• Epithelium: Initially transitional epithelium (urothelium), which may transition to pseudostratified columnar in lower regions.

• Surrounding tissue: Embedded entirely within the substance of the prostate gland, encased by fibromuscular and glandular tissues.

4. Function

The prostatic urethra performs dual functions:

• Urinary function: Conducts urine from the bladder toward the membranous and penile urethra for elimination.

• Reproductive function: Transmits semen during ejaculation, receiving contributions from the prostate and ejaculatory ducts.

5. Physiological Role(s)

The prostatic urethra plays an important role in several physiological processes:

• Urine and semen separation: During ejaculation, the internal urethral sphincter contracts to prevent retrograde semen flow into the bladder (especially important in males).

• Transport of secretions: Facilitates the delivery of prostatic fluid and sperm components into the urethral lumen.

• Interaction with prostate function: As prostatic secretions contribute to semen volume and fertility, the prostatic urethra acts as a conduit and coordination point.

6. Clinical Significance

Benign Prostatic Hyperplasia (BPH)

In older men, the prostate often enlarges, compressing the prostatic urethra and leading to lower urinary tract symptoms (LUTS):

• Hesitancy

• Weak stream

• Incomplete emptying

• Nocturia and urgency

Treated with medications (e.g., alpha-blockers, 5-alpha reductase inhibitors) or surgical procedures such as TURP (transurethral resection of the prostate).

Prostate Cancer

Prostate cancer may affect the tissue surrounding the prostatic urethra. Advanced or centrally located tumors may invade the urethral wall, leading to urinary obstruction or hematuria.

Urethral Stricture

Scarring or narrowing of the prostatic urethra (often post-surgical or due to chronic inflammation) can restrict urine flow. May require dilatation, endoscopic urethrotomy, or stenting.

Retrograde Ejaculation

Disruption of the internal urethral sphincter (e.g., after prostate surgery) can lead to semen flowing backward into the bladder instead of forward through the prostatic urethra. This affects fertility but is generally harmless.

Catheterization Considerations

Understanding the anatomy of the prostatic urethra is important during catheterization or cystoscopy to avoid trauma. Angulation at the bladder neck must be navigated carefully, especially in older patients.

Imaging and Endoscopy

The prostatic urethra is assessed via:

• Cystourethroscopy: Direct visualization of the lumen and associated structures (e.g., verumontanum).

• Retrograde urethrogram (RUG): For evaluating strictures or trauma.

• TRUS (transrectal ultrasound): For evaluating prostate volume and pathology.