Muscle
Bulbospongiosus
A superficial perineal muscle acting on erectile tissue
High-yield
Compression of the penile bulb helps clear the spongy urethra and expel semen. Around the vestibule, the muscle compresses the bulbs and narrows the vaginal opening.
Overview
Bulbospongiosus lies over the penile bulb or paired vestibular bulbs. In the male, its halves meet over the bulb at a median raphe. In the female, the vaginal opening separates the two muscles. Connections to the perineal body link it mechanically to neighboring perineal structures.
Reference facts
- Origin
- Arises from the perineal body and adjacent fascia; male fibers also attach to a midline raphe over the bulb.
- Insertion
- Attaches to the perineal membrane and erectile-tissue fascia: around the spongiosum and penile root in males, and toward the clitoral bodies in females.
- Innervation
- Motor supply is through deep muscular branches of the perineal nerve from the pudendal nerve, S2–S4.
- Action
- Compresses underlying erectile tissue, assists erection, and in males helps expel urethral contents; in females it contributes to narrowing the vaginal opening.
- Blood supply
- Supplied by perineal branches of the internal pudendal artery, with adjacent bulb branches contributing.
Clinical correlation
Perineal injury may disrupt the muscle or its attachment to the perineal body. Its reflex contraction forms part of the bulbocavernosus reflex, which assesses sacral sensory and motor circuitry involving S2–S4.
Frequently asked questions
What does the bulbospongiosus do?
Compresses underlying erectile tissue, assists erection, and in males helps expel urethral contents; in females it contributes to narrowing the vaginal opening.
What nerve innervates the bulbospongiosus?
The bulbospongiosus is innervated by the motor supply is through deep muscular branches of the perineal nerve from the pudendal nerve, S2–S4.
Where does the bulbospongiosus attach?
Origin: Arises from the perineal body and adjacent fascia; male fibers also attach to a midline raphe over the bulb. Insertion: Attaches to the perineal membrane and erectile-tissue fascia: around the spongiosum and penile root in males, and toward the clitoral bodies in females.
What is the blood supply of the bulbospongiosus?
The bulbospongiosus is supplied by the supplied by perineal branches of the internal pudendal artery, with adjacent bulb branches contributing.