The inner part, attached to the bony margins of the pubic arch (that part of the pelvis directly in front and at the base of the trunk), is called the root of the penis.

The root of the penis comprises two crura, or projections, and the bulb of the penis. The oval bulb of the penis lies between the two crura and is covered by the bulbospongiosus muscle. The crura and the bulb are attached respectively to the edges of the pubic arch and to the perineal membrane (the fibrous membrane that forms a floor of the trunk).
A deep fascia, or sheet of connective tissue, surrounding the structures in the body of the penis is prolonged to form the suspensory ligament, which anchors the penis to the pelvic bones at the midpoint of the pubic arch. The skin of the scrotum is thin, pigmented, devoid of fatty tissue, and more or less folded and wrinkled.
This condition arises because the right corpus cavernosum and the left corpus cavernosum, the masses of erectile tissue, lie close together in the dorsal part of the penis, while a single body, the corpus spongiosum, which contains the urethra, lies in a midline groove on the undersurface of the corpora cavernosa.