Bulbospongiosus muscle

The bulbospongiosus is a paired superficial perineal muscle located in the urogenital triangle. It differs anatomically between males and females but serves related functions involving urethral compression, ejaculation, clitoral erection, and stabilization of pelvic structures. It overlies erectile tissues—specifically, the bulb of the penis in males and the bulb of the vestibule in females. It is innervated by the deep branch of the perineal nerve (from the pudendal nerve, S2–S4).

Structure

The bulbospongiosus is a striated muscle made of skeletal fibers. It varies slightly in morphology between sexes but maintains a similar pattern of origin, insertion, and layered organization within the superficial perineal pouch.

Origin and Insertion

• Origin: Perineal body (central tendon of perineum)
• Insertion (male): Perineal membrane and corpus spongiosum of penis
• Insertion (female): Pubic arch, fascia of corpora cavernosa, and bulb of vestibule

Differences by Sex

• Male: Single midline muscle wrapping around the bulb of the penis and proximal corpus spongiosum
• Female: Bilateral muscles flanking the vestibule of the vagina, surrounding the bulb of the vestibule and greater vestibular glands

Location

The bulbospongiosus muscle is situated within the superficial perineal pouch of the urogenital triangle, superficial to the perineal membrane.

Function

• Male:
  • Compresses bulb of penis during ejaculation and urination
  • Aids in emptying urethra of residual urine or semen
  • Contributes to erection by compressing deep dorsal vein of penis
• Female:
  • Compresses greater vestibular glands during sexual arousal
  • Tenses vagina and contributes to clitoral erection

Innervation

• Deep branch of perineal nerve (branch of pudendal nerve, S2–S4)

Blood Supply

• Perineal branches of the internal pudendal artery

Clinical Significance

• Perineal trauma: Can be involved in obstetric tears (females)
• Dysfunction: Weakness or hypertonicity may contribute to sexual dysfunction or pelvic floor disorders
• Surgical landmark: Important during repair of perineal tears and urogenital surgeries