The bulb of vestibule consists of a mass of erectile tissue lying on either side of the vagina. It is a structure which is composed of two halves, right and left, which get fused together by means of a small and narrow intermediate part situated between the clitoris and the orifice of the urethra. Laterally and inferiorly, each half of the bulb is covered by the bulbospongiosus muscle.
Each of the two halves is a dense venous plexus (mass of blood vessels) whose elongated lateral portions are embedded in the base of the labia majora. Posteriorly, each half is also thicker than the anterior region, covering the greater vestibular gland. The bulb of the vestibule has a tunica albuginea investing the venous plexus, which is pierced by smooth muscle fibers and connective tissue bundles.
Each half of the bulb rests against the lateral (external) wall of the vagina, lying superficially to the triangular ligament. It corresponds to the bulb portions of the corpus spongiosum of the male. It receives oxygenated blood from a secondary branch of the internal pudendal artery.
Below, schematic drawing showing the bulb of vestibule of vagina and other external parts of the female reproductive organs
