Fibers
Its fibers diverge like the barbs of a quill-pen; the most posterior form a thin layer, which is lost on the inferior fascia of the urogenital diaphragm; the middle fibers encircle the bulb and adjacent parts, of the corpus cavernosum urethræ, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethræ, in a strong aponeurosis; the anterior fibers, spread out over the side of the corpus cavernosum penis, to be inserted partly into that body, anterior to the Ischiocavernosus, occasionally extending to the pubis, and partly ending in a tendinous expansion which covers the dorsal vessels of the penis.
The latter fibers are best seen by dividing the muscle longitudinally, and reflecting it from the surface of the corpus cavernosum urethræ.
Read more about this topic: Bulbospongiosus Muscle