Musculus bulbospongiosus
The bulbospongiosus is a striated perineal muscle. In the stallion or gelding it is an unpaired midline muscle that originates from the perineal body and median raphe and surrounds the bulb of the penis and proximal urethra, continuing along the penile urethra. It produces the pulsatile contractions of ejaculation and helps empty residual urine after urination. In the mare the homologous muscle (constrictor vestibuli) encircles the vestibule and can constrict it. Innervation is via the pudendal nerve (S2–S4 range). Clinically, it is rarely a primary disease focus but is relevant in perineal trauma, breeding injuries, or assessment of the male reproductive tract. Its action can be observed during urination or ejaculation.
Origin: Perineal body and median raphe
Insertion: Surrounds the bulb of the penis (male) or vestibule (female)
Action: Male: expels semen during ejaculation and residual urine after urination. Female: constricts the vestibule
Innervation: Pudendal nerve (S2-S4)
Part of the pelvic floor and penile musculature. Relevant in evaluation of ejaculatory function or perineal lacerations.
## Overview Urospermia is contamination of semen with urine, producing yellowish semen with an ammonia odor and poor fertility. It can result from ejaculatory dysfunction, including damage to the bul
Difficulty urinating, blood in the urine, or breeding injuries in stallions should be evaluated promptly. Perineal swelling after foaling or breeding warrants veterinary examination.
## Overview Urospermia is contamination of semen with urine, producing yellowish semen with an ammonia odor and poor fertility. It can result from ejaculatory dysfunction, including damage to the bulbospongiosus muscle from pudendal nerve injury. Incomplete ejaculation and post-urination dribbling may also occur. ## Causes Neurologic dysfunction, bladder-neck incompetence, or behavioral issues. ## Diagnosis Semen evaluation showing urine contamination and assessment of ejaculatory function. ## Treatment Management of collection technique, medications to improve bladder-neck tone, and treatment of underlying nerve damage if present. Fertility is often reduced. ## Recovery and Prognosis Guarded for consistent fertility. ## Prevention Careful handling to avoid pudendal nerve injury. Signs include: urine-contaminated semen (yellowish, ammonia odor); poor fertility; incomplete ejaculation; dribbling of urine after urination
Part of the pelvic floor and penile musculature. Relevant in evaluation of ejaculatory function or perineal lacerations.
Difficulty urinating, blood in the urine, or breeding injuries in stallions should be evaluated promptly. Perineal swelling after foaling or breeding warrants veterinary examination.
See the Bulbospongiosus on our interactive 3D horse model. Open 3D Model