Spongy Penile Urethra

1. Overview

The spongy urethra—also known as the penile urethra—is the longest segment of the male urethra, extending through the length of the penis. It serves as a shared conduit for urine and semen, playing an integral role in both the urinary and reproductive systems. It is encased within the corpus spongiosum, a vascular erectile tissue that protects and supports the urethral lumen during erection and ejaculation.

2. Location

The spongy urethra is located in the anterior segment of the male urethra, beginning at the external urethral sphincter (where the membranous urethra ends) and terminating at the external urethral meatus at the tip of the glans penis. It is entirely surrounded by the corpus spongiosum, which prevents its compression during erection.

Divisions within the spongy urethra include:

• Bulbar urethra: The proximal widened portion located in the bulb of the penis.

• Penile shaft segment: Runs longitudinally through the body of the penis.

• Fossa navicularis: Slightly dilated distal portion within the glans penis, just before the external meatus.

3. Structure

The spongy urethra is approximately 15–16 cm in length and is lined by a variable epithelial covering:

• Proximal portion: Pseudostratified columnar epithelium.

• Distal portion (fossa navicularis): Stratified squamous epithelium.

Key structural features include:

• Corpus spongiosum: Vascular erectile tissue surrounding the urethra, cushioning and protecting it.

• Lumenal shape: Normally collapsed but distensible during urination or ejaculation.

• Mucous glands: Small urethral (Littre’s) glands secrete mucus to lubricate the lumen.

4. Function

The spongy urethra has dual roles in the excretory and reproductive systems:

• Urine conduit: Transports urine from the bladder to the external urethral meatus during micturition.

• Semen conduit: Transmits semen during ejaculation, receiving secretions from the prostate and bulbourethral glands upstream.

• Lubrication: Mucosal secretions assist in maintaining urethral patency and reducing friction during ejaculation.

5. Physiological Role(s)

In addition to mechanical transport, the spongy urethra contributes to several physiological processes:

• Maintains urethral patency: The corpus spongiosum prevents collapse during erection or ejaculation.

• Lubrication and protection: Mucus from Littre’s glands protects epithelial lining from acidic urine and sperm components.

• One-way flow control: Coordinated with urethral sphincters and erectile tissue to separate urine and semen discharge.

6. Clinical Significance

Urethral Stricture

Scarring or fibrosis of the spongy urethra (especially post-catheterization, trauma, or infection) may result in narrowing of the lumen. Symptoms include:

• Decreased urine stream

• Straining or incomplete emptying

• Recurrent urinary tract infections

Diagnosis is confirmed by retrograde urethrogram; treatment includes urethral dilation, urethrotomy, or surgical reconstruction.

Hypospadias

A congenital defect where the external urethral meatus opens on the ventral surface of the penis due to incomplete closure of the spongy urethra. Surgical correction is typically performed during infancy or childhood.

Urethritis

Infection of the spongy urethra (often sexually transmitted, e.g., gonorrhea or chlamydia) presents with:

• Dysuria (painful urination)

• Urethral discharge

Treated with appropriate antibiotics depending on the pathogen.

Penile Trauma

Blunt or penetrating trauma can result in urethral rupture or false passage. The spongy urethra is especially vulnerable during:

• Straddle injuries

• Improper catheterization

Management includes urethral repair and catheter drainage.

Urethral Carcinoma

Though rare, cancer of the spongy urethra may present with:

• Bleeding from the urethral meatus

• Obstructive urinary symptoms

Diagnosed by urethroscopy and biopsy, often requiring surgical resection.

Instrumentation Relevance

Knowledge of the length, curvature, and diameter of the spongy urethra is essential during:

• Catheterization

• Cystoscopy

• Endoscopic procedures

Careful technique avoids trauma and long-term stricture formation.