Which muscle compresses the crus of the penis?

• A. Bulbospongiosus
• B. Ischiocavernosus
• C. Superficial transverse perineal
• D. External anal sphincter

Answer: (B)

Ischiocavernosus is the muscle that lies around the crura of the penis and actively compresses them. When it contracts, it squeezes the crura of the corpora cavernosa, increasing intracavernosal pressure and helping to maintain penile rigidity by restricting venous outflow through the deep dorsal veins. This action is essential for achieving and sustaining erection. The muscle is innervated by the perineal branch of the pudendal nerve.

In contrast, the bulbospongiosus mainly surrounds the bulb of the penis and acts on the proximal erectile tissue of the corpus spongiosum, contributing to erection and ejaculation differently; the superficial transverse perineal is a perineal floor muscle with no direct role in compressing the crus, and the external anal sphincter controls the anal canal rather than penile erection.