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Tunica albuginea (penis)

The tunica albuginea of the penis is a dense fibrous connective tissue layer that surrounds the erectile tissues of the penis, providing strength, rigidity, and structural support. It encases both corpora cavernosa and the corpus spongiosum, playing a critical role in erection mechanics by trapping venous blood within the erectile bodies.

The tunica albuginea is clinically important in penile trauma, erectile dysfunction, and Peyronie’s disease, where fibrous thickening of this structure leads to penile curvature.

Synonyms

  • Penile tunica albuginea

  • Fibrous envelope of corpora cavernosa

  • Albuginea of penis

Structure and Layers

  • Composed of dense collagen fibers with some elastic tissue

  • Bilaminar organization in corpora cavernosa:

    • Inner circular layer: Surrounds each corpus cavernosum individually

    • Outer longitudinal layer: Encases both corpora cavernosa together

  • Corpus spongiosum covering: Tunica albuginea here is thinner and more elastic compared to that around the corpora cavernosa

Relations

  • External: Covered by the deep fascia of the penis (Buck’s fascia)

  • Internal: Encases corpora cavernosa and corpus spongiosum

  • Proximally: Continuous with tunica of crura and penile root

  • Distally: Extends toward the glans but thins significantly

Function

  • Provides rigid structural support to corpora cavernosa during erection

  • Facilitates veno-occlusive mechanism, preventing venous outflow and sustaining erection

  • Protects erectile tissue from rupture during sexual activity

  • Maintains penile shape and stability

Clinical Significance

  • Penile fracture: Rupture of the tunica albuginea, usually during trauma in erection

  • Peyronie’s disease: Fibrotic thickening or plaque formation within the tunica, causing curvature, pain, and erectile dysfunction

  • Surgical importance: Landmark in penile prosthesis implantation, trauma repair, and reconstructive surgery

  • Imaging relevance: Essential to evaluate in MRI/ultrasound for suspected trauma, fibrosis, or tumors

MRI Appearance

T1-weighted images:

  • Tunica albuginea appears as a low-signal intensity thin line surrounding erectile tissue

  • Adjacent fat and corpora provide contrast

T2-weighted images:

  • Tunica albuginea remains low signal

  • Fibrosis or plaque (Peyronie’s disease) may appear as focal low-signal thickening

STIR (Short Tau Inversion Recovery):

  • Normal tunica remains low signal

  • Inflammatory or edematous changes may appear with bright hyperintensity adjacent to tunica

T1 Fat-Sat Post-Contrast:

  • Normal tunica enhances minimally, if at all

  • Plaques or inflammatory changes show focal or heterogeneous enhancement

3D T2 SPACE / CISS:

  • Tunica albuginea appears as a thin hypointense rim sharply delineating corpora cavernosa and corpus spongiosum

  • Provides excellent contrast with bright fluid and intermediate erectile tissue

CT Appearance

Non-Contrast CT:

  • Tunica albuginea is not well differentiated; penile contour maintained by dense fibrous rim

  • Penile fracture may appear as contour defect or hematoma breaching tunica boundary

Post-Contrast CT:

  • Tunica itself does not enhance

  • Surrounding hematomas, vascular injuries, or inflammation enhance variably

  • Useful mainly in acute trauma with associated pelvic injury

MRI image

Tunica albuginea (penis) mri axial anatomy image-img-00000-00000_00001

MRI image

Tunica albuginea (penis) mri coronal image