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Bulbospongiosus muscle (Male)

The bulbospongiosus muscle is a paired superficial perineal muscle of the male perineum that partially surrounds the bulb of the penis. It plays an important role in sexual and urinary function by contributing to erection, ejaculation, and expulsion of the last drops of urine. It lies within the superficial perineal pouch and is covered by the superficial perineal fascia. Its contraction compresses the bulb of the penis and underlying erectile tissue.

Synonyms

  • Bulbocavernosus muscle

  • Superficial perineal bulb muscle

  • Muscle of the penile bulb

Origin, Course, and Insertion

  • Origin: Arises from the perineal body (central tendon of perineum) and the median raphe over the bulb of the penis

  • Course: Fibers pass forward, surrounding the bulb and proximal corpus spongiosum, and run along the ventral penis

  • Insertion: Fibers insert into the dorsal penile aponeurosis, the perineal membrane, and fascia of the corpora cavernosa; anterior fibers interlace with those of the contralateral side

Relations

  • Anteriorly: Corpus cavernosum of penis

  • Posteriorly: Perineal body and external anal sphincter

  • Laterally: Ischiocavernosus muscles and superficial transverse perineal muscles

  • Superiorly: Perineal membrane and corpus spongiosum

  • Inferiorly: Superficial perineal fascia and skin of perineum

Function

  • Compresses the bulb of the penis to empty urethra of urine and semen

  • Contributes to ejaculation by rhythmic contractions

  • Assists in penile erection by compressing deep dorsal vein of penis, maintaining venous engorgement

  • Supports pelvic floor and perineal structures

Clinical Significance

  • Plays a role in erectile function and ejaculation; dysfunction can contribute to sexual disorders

  • Involved in perineal trauma, urethral injury, or surgical repair in urology

  • Can be a site of infection or involvement in perineal abscess

  • May be evaluated in pelvic floor dysfunction studies using MRI

MRI Appearance

T1-weighted images:

  • Muscle appears as low-to-intermediate signal intensity band around bulb of penis

  • Adjacent fat appears bright, outlining the muscle

T2-weighted images:

  • Low-to-intermediate signal muscle fibers

  • Hyperintense signal may be seen with edema or inflammation

STIR (Short Tau Inversion Recovery):

  • Normal muscle remains low-to-intermediate signal

  • Pathological processes (inflammation, trauma) show bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal muscle shows mild homogeneous enhancement

  • Inflammation, infection, or neoplasm may enhance more intensely or heterogeneously

CT Appearance

Non-Contrast CT:

  • Muscle appears as soft tissue density band in perineum around bulb of penis

  • Hematomas or calcifications may be seen as localized high-density areas

Post-Contrast CT:

  • Muscle shows mild homogeneous enhancement normally

  • Abscesses or infection show rim enhancement with central low attenuation

  • Tumor or fibrosis may appear as irregular enhancing soft tissue mass

MRI image

CT image

Bulbospongiosus muscle (Male) CT axial anatomy image-img-00000-00000