Rigi10™ Malleable Penile Prosthesis
Also Known As
Bulbocavernosus muscle, Musculus bulbospongiosus, BS muscle
Definition
The bulbospongiosus muscle is a paired, superficial muscle of the pelvic floor, located in the superficial perineal space.¹ It exhibits sexual dimorphism, meaning its structure and specific attachments differ between males and females. In males, the muscle fibers are fused at a median raphe and surround the bulb of the penis and the corpus spongiosum.¹ In females, the two parts of the muscle are separate and flank the vaginal orifice, covering the bulbs of the vestibule.¹
The primary function of the bulbospongiosus muscle involves the compression of the erectile tissues it surrounds and structures within the urogenital tract. In males, it plays a crucial role in several physiological processes: it aids in the expulsion of residual urine from the urethra after micturition,² contributes to ejaculation by propelling semen through the urethra,¹ and assists in achieving and maintaining penile erection by compressing the bulb of the penis and the deep dorsal vein of the penis, thereby impeding venous outflow.¹³ In females, the bulbospongiosus muscle contributes to the erection of the clitoris by compressing its deep dorsal vein, constricts the vaginal orifice, and aids in emptying the greater vestibular (Bartholin’s) glands.¹² In both sexes, it also provides support to the perineal body.¹
Clinical Context
The bulbospongiosus muscle is clinically relevant in several contexts related to urogenital function and dysfunction. Its role in urinary continence is significant, as it helps to expel the last drops of urine from the urethra, preventing post-void dribbling.¹ Dysfunction of this muscle can contribute to urinary symptoms. In males, the bulbospongiosus muscle is integral to sexual function, including erection and ejaculation.¹³ Its proper function is necessary for compressing the penile bulb and crura, which aids in achieving and maintaining rigidity and in the forceful expulsion of semen. Therefore, damage to this muscle or its innervation (e.g., due to trauma, surgery, or neurological conditions) can lead to erectile dysfunction or ejaculatory disorders. For instance, during perineal surgeries, such as radical prostatectomy or urethroplasty, care must be taken to preserve the integrity of the bulbospongiosus muscle and its nerve supply (branches of the pudendal nerve) to minimize the risk of postoperative sexual or urinary dysfunction.¹
In females, the bulbospongiosus muscle contributes to sexual arousal by aiding in clitoral erection and constricting the vaginal opening.¹ Its involvement in the function of the greater vestibular glands also means that issues with this muscle could potentially affect glandular secretions. During childbirth, the perineal musculature, including the bulbospongiosus, can be subject to stretching or tearing, which may require repair and can have implications for postpartum recovery and pelvic floor function.¹
Assessment of bulbospongiosus muscle function can be part of a comprehensive pelvic floor examination, particularly when investigating causes of sexual dysfunction, urinary incontinence, or pelvic pain. Electromyography (EMG) can be used to assess the electrical activity of the muscle, and imaging techniques like MRI can visualize its structure. Expected outcomes following interventions that affect this muscle (e.g., pelvic floor rehabilitation, surgical repair) aim to restore or improve its contribution to normal urinary and sexual function.