In male anatomy, the corpus spongiosum of penis is a mass of erectile tissue that lies along the underside of the penis and is located below the pair of corpus cavernosa, which contain 90 percent of the blood volume during a normal erection. It is a smaller region compared to either of the identical corpus cavernosa.
The three groups of tissues, the two cavernosa and the spongiosum, are expandable, sponge-like structures involved in the process of a penile erection.
The corpus spongiosum penis corresponds to the female vestibular bulbs. It contains the urethra, the tube through which urine and semen exit the body, and extends to form the glans penis, an expanded cap at the tip of the penis. The corpus spongiosum penis may be described as enclosing the urethra and ends at the vertical urethral orifice. This third mass of tissue mainly prevents compression of the urethra during penile erection.