The bulb of the penis is the bottom portion, or base, of the penis. The bulb is located just above the testicles. It contributes to the shape of the penis.
The bulb of the penis is composed of a large bundle of tissue. Together with other components, the bulb forms the internal structure of the penis, as well as the visible, external shape. The bulb appears as a prominent ridge on the shaft of the penis.
This tissue mass expands due to the muscle known as the corpus spongiosum. This corpus spongiform is attached to the perineal membrane that extends from the perineum, the area between the scrotum and anus.
From the bulb of the penis, the corpus spongiform travels up toward the urethra to form the glans at the top of the penis. The urethra, the tube through which urine and semen exit the body, extends from the bulb. The surface of the bulb is surrounded by bulbospongiosus muscle.
The internal pudendal vein drains blood from the bulb, while the internal pudendal artery supplies the bulb of penis with blood.
The bulb of the vestibule, similar to the bulb of the penis, is present in people with female reproductive organs.