Male - Corpus Cavernosum

1. Overview

The corpus cavernosum refers to one of the two cylindrical erectile tissues that run along the length of the penis. These paired structures are primarily responsible for penile erection, allowing rigidity and penetration during sexual intercourse. Their ability to engorge with blood is essential for sexual function and reproductive capability in males. The plural form is "corpora cavernosa."

2. Location

The corpora cavernosa are located dorsally (on the top side) of the penis when in the anatomical position. Each corpus cavernosum extends from the penile root (crura) near the pubic symphysis to the glans penis. They lie side-by-side, separated by a fibrous septum, and are surrounded by a dense fibrous covering called the tunica albuginea. The third erectile body, the corpus spongiosum, lies ventrally between them and contains the urethra.

3. Structure

Each corpus cavernosum is composed of the following:

• Trabeculae: A network of smooth muscle and fibrous tissue forming the internal framework.

• Cavernous spaces (sinusoids): Vascular spaces that fill with blood during erection.

• Tunica albuginea: A thick fibrous capsule that surrounds the corpus cavernosum and helps maintain pressure during erection.

• Arterial supply: Primarily from the deep arteries of the penis (branches of the internal pudendal artery).

• Venous drainage: Blood is drained through the emissary veins into the deep dorsal vein of the penis.

At the base of the penis, each corpus cavernosum diverges into a structure called the crus of the penis, which is anchored to the ischiopubic ramus.

4. Function

The main function of the corpora cavernosa is:

• Penile erection: During sexual arousal, the corpora fill with blood and become rigid, enabling penetration during intercourse.

• Support: Provide structural rigidity to the penis during erection and serve as a mechanical lever for sexual activity.

5. Physiological Role(s)

The corpus cavernosum plays a vital role in male sexual function:

• Erection mechanism: Parasympathetic stimulation (via pelvic splanchnic nerves) leads to the release of nitric oxide (NO), which relaxes smooth muscle in the trabeculae and dilates arteries, increasing blood flow into the sinusoids.

• Venous occlusion: Expansion of the corpora compresses the venous outflow, trapping blood and maintaining the erection.

• Detumescence: After orgasm or cessation of arousal, sympathetic stimulation contracts trabecular smooth muscle and opens venous channels, allowing blood to exit and the penis to return to a flaccid state.

6. Clinical Significance

Disorders involving the corpora cavernosa can significantly impact sexual and reproductive health:

• Erectile dysfunction (ED): Inability to achieve or maintain an erection often results from impaired blood flow, nerve damage, or dysfunction within the corpora. Common causes include atherosclerosis, diabetes, trauma, or psychogenic factors.

• Peyronie’s disease: Fibrous plaque formation within the tunica albuginea causes curvature of the penis, often painful and associated with erectile dysfunction.

• Priapism: A prolonged, painful erection not related to sexual stimulation, often due to blood not draining from the corpora cavernosa. It requires urgent intervention to prevent permanent tissue damage.

• Trauma or fracture: A penile fracture occurs when the tunica albuginea is torn during vigorous sexual activity or trauma, often accompanied by a "popping" sound, swelling, and pain. Surgical repair is usually required.

• Injection therapy and implants: In severe cases of ED, vasoactive agents may be injected directly into the corpora, or penile prostheses may be surgically implanted within them.

Assessment of corpora cavernosa function is vital in urology, especially in cases of erectile dysfunction or genital trauma. Doppler ultrasound and nocturnal penile tumescence testing are common diagnostic tools.