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Bulbospongiosus muscle (Female)

The bulbospongiosus muscle in females is a paired superficial perineal muscle forming part of the pelvic floor and urogenital triangle. It surrounds the vestibular bulbs and greater vestibular glands and contributes to the sphincteric mechanism of the vaginal and urethral orifices. Unlike in males, where it covers the bulb of the penis, in females it is split into two halves by the vaginal orifice, forming a muscular sheath on either side of the vaginal vestibule.

This muscle plays important roles in sexual function, micturition, and continence, and is also relevant in gynecological surgery and pelvic floor imaging.

Synonyms

  • Bulbocavernosus muscle (female)

  • Female bulbospongiosus

  • Superficial perineal sphincter

Origin, Course, and Insertion

  • Origin: Arises from the perineal body and the median raphe of the perineum

  • Course: Fibers run anteriorly and laterally, surrounding the vaginal vestibule and the bulbs of the vestibule; some fibers cross the midline anteriorly

  • Insertion: Insert into the fascia of the clitoris and dorsum of the clitoral body

Relations

  • Anteriorly: Clitoris

  • Posteriorly: Perineal body and external anal sphincter

  • Laterally: Vestibular bulbs and greater vestibular glands (Bartholin’s glands)

  • Medially: Vaginal vestibule and orifice

Function

  • Acts as a sphincter of the vaginal orifice, narrowing the vaginal opening during contraction

  • Compresses the vestibular bulbs, contributing to erectile function and sexual response

  • Assists in emptying the urethra and vestibular glands

  • Provides support to pelvic floor structures

Clinical Significance

  • Involved in female sexual dysfunction and dyspareunia if weakened or damaged

  • Can be disrupted in obstetric trauma or episiotomy

  • Targeted in pelvic floor rehabilitation and strengthening exercises

  • May be evaluated in MRI for pelvic floor disorders, perineal tears, or Bartholin’s gland pathology

MRI Appearance

T1-weighted images:

  • Normal muscle shows low-to-intermediate signal intensity

  • Fat within surrounding perineal tissue appears bright

  • No fluid: muscle margins are clearly defined

T2-weighted images:

  • Normal muscle demonstrates low-to-intermediate signal intensity

  • Vaginal or vestibular secretions and any fluid collections appear bright

  • Fat surrounding the muscle appears relatively bright

STIR (Short Tau Inversion Recovery):

  • Normal muscle shows low-to-intermediate signal

  • Fluid, edema, or inflammation within or around the muscle appears bright

  • Fat signal is suppressed and appears dark

T1 Fat-Sat Post-Contrast:

  • Normal muscle shows mild homogeneous enhancement

  • Inflammation, infection, or tumor infiltration enhances irregularly

  • Abscess appears with rim enhancement and central non-enhancing fluid

CT Appearance

Non-Contrast CT:

  • Appears as soft tissue density within the perineum

  • Surrounded by fat planes, which appear as low density

  • Pathology (hematoma, abscess) may be hyperdense or hypodense relative to muscle

Post-Contrast CT:

  • Normal muscle enhances mildly and uniformly

  • Abscesses demonstrate rim enhancement with central low density

  • Tumor infiltration or inflammation shows irregular enhancement

MRI image

Bulbospongiosus muscle female MRI axial anatomy image-img-00000-00000

MRI image

Bulbospongiosus muscle female MRI sagitttal anatomy image-img-00000-00000

CT image

Bulbospongiosus muscle female ct axial anatomy image-img-00000-00000