The bulbospongiosus is a perineal muscle with sex-specific anatomy and function, forming the superficial perineal pouch alongside the ischiocavernosus. In males it covers the bulb of the penis and compresses the corpus spongiosum during ejaculation, propelling semen through the urethra. In females it surrounds and constricts the vaginal opening. The bulbocavernosus reflex tests S2-S4 sacral arc integrity by squeezing the glans and feeling for anal sphincter contraction.
| Origin | Central perineal tendon (perineal body) and median raphe over the bulb of the penis; Perineal body (central tendon of the perineum) |
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| Insertion | Dorsal surface of the penis and corpus spongiosum; Clitoral body and perineal membrane |
| Nerve Supply | Perineal branch of the pudendal nerve (S2, S3, S4) |
| Blood Supply | Perineal artery |
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The muscle expulsion of residual urethral contents after voiding (post-micturition dribble) is caused by bulbospongiosus weakness in men, and its strengthening through pelvic floor exercises reduces this common complaint.
The bulbocavernosus reflex, tested by squeezing the glans or clitoris (or tugging an indwelling catheter) and feeling the anal sphincter contract, assesses the S2-S4 reflex arc; it is absent in conus and cauda equina lesions and during spinal shock, and its return after spinal shock in a cord injury signals the end of that phase. In women the muscle (also called bulbocavernosus) surrounds the vaginal opening over the vestibular bulbs and is torn in second-degree and more severe perineal tears, so it is re-approximated during episiotomy and perineal body repair. Involuntary spasm of the bulbospongiosus and other pelvic floor muscles contributes to vaginismus, which is treated with pelvic floor physiotherapy and sometimes botulinum toxin.
Not accessible to external palpation due to perineal position. BCR is tested clinically by the reflex examination.
Bulbospongiosus weakness producing incomplete urethral emptying after voiding in men, managed with pelvic floor strengthening exercises.
Other versions of this entry: Bulbospongiosus (Full) · Bulbospongiosus Detail
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