Male - Corpus Spongiosum

1. Overview

The corpus spongiosum is one of the three erectile tissues of the penis and plays a vital role in male sexual and reproductive function. Unlike the paired corpora cavernosa, the corpus spongiosum is unpaired and surrounds the penile urethra. Its primary role is to maintain the patency of the urethra during erection and ejaculation, ensuring the unimpeded passage of semen and urine.

2. Location

The corpus spongiosum lies on the ventral (underside) aspect of the penis, in the midline, between the two corpora cavernosa. It begins as the bulb of the penis at the base (root), expands distally to form the glans penis, and runs the entire length of the penile shaft, enclosing the spongy (penile) urethra.

3. Structure

The corpus spongiosum has the following structural features:

• Erectile tissue: Contains trabeculae of smooth muscle and connective tissue enclosing vascular spaces (sinusoids) that engorge with blood during erection.

• Penile urethra: Traverses the corpus spongiosum from the bulb to the external urethral orifice at the tip of the glans.

• Glans penis: The distal expansion of the corpus spongiosum forms the conical glans, which covers the distal ends of the corpora cavernosa.

• Fibrous covering: Surrounded by a thinner tunica albuginea than that of the corpora cavernosa, allowing it to remain more compressible during erection.

The corpus spongiosum receives blood supply from branches of the internal pudendal artery, including the bulbourethral artery, and is drained by corresponding veins.

4. Function

The corpus spongiosum has several key functions:

• Protects and supports the urethra: Maintains the patency of the urethral canal during erection, preventing it from being compressed shut.

• Contributes to erection: Engorges with blood during sexual arousal, though to a lesser degree than the corpora cavernosa, allowing flexibility and cushioning.

• Forms the glans penis: The glans is critical for sexual sensation and the delivery of semen during ejaculation.

5. Physiological Role(s)

The corpus spongiosum participates in several important physiological processes:

• Urethral function during erection: While the corpora cavernosa become rigid, the corpus spongiosum remains softer to keep the urethral lumen open for the passage of semen.

• Sexual arousal and ejaculation: Engorges with blood during arousal and helps coordinate the pressure needed for forceful ejaculation.

• Sensory input: The glans penis, part of the corpus spongiosum, contains dense sensory innervation important for orgasm and sexual satisfaction.

The corpus spongiosum is responsive to parasympathetic stimulation (via pelvic splanchnic nerves) during erection and contributes to the overall mechanics of copulation and ejaculation.

6. Clinical Significance

The corpus spongiosum can be involved in several medical conditions:

• Urethral stricture: Scarring or narrowing of the urethra within the corpus spongiosum can impair urine flow or ejaculation, often requiring dilation or surgical repair.

• Peyronie’s disease (less commonly): While primarily affecting the corpora cavernosa, severe fibrous plaque formation can involve the corpus spongiosum, especially at the glans.

• Trauma or penile fracture: Blunt trauma can damage the corpus spongiosum and urethra, especially during forceful intercourse or injury; symptoms may include blood at the urethral meatus and urinary difficulty.

• Hypospadias and epispadias: Congenital malformations affecting the urethral opening, often associated with abnormal development of the corpus spongiosum and glans.

• Urethritis: Infections of the urethra (e.g., gonorrhea, chlamydia) inflame the surrounding corpus spongiosum, causing pain and discharge.

• Priapism (less common): While priapism primarily involves the corpora cavernosa, involvement of the corpus spongiosum may occur in prolonged cases and require urgent decompression to avoid ischemia.

Assessment of the corpus spongiosum is important in urology and sexual medicine, particularly in evaluating erectile function, urinary problems, or structural abnormalities. Imaging, cystoscopy, and urethral calibration are often used for diagnosis.