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 |
| Actions | Male: expels the last drops of urine and semen; assists erection by compressing the corpus spongiosum; Female: constricts the vaginal orifice and assists in clitoral erection |
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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 (BCR), tested by squeezing the glans or clitoris and feeling anal wink contraction, assesses S2-S4 reflex arc integrity — absent BCR in spinal cord injury below the conus indicates complete lower motor neurone injury with flaccid paralysis. BCR return after spinal shock indicates upper motor neurone injury with return of reflex activity below the level. Vaginismus involves involuntary bulbospongiosus and pelvic floor spasm that prevents vaginal penetration.
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.
