Corpus spongiosum penis
In male anatomy, the corpus spongiosum penis is a mass of erectile tissue that lies along the bottom of the penis and located below the pair of corpus cavernosa, which contains 90 percent of the blood during a normal erection. It is a smaller region compared to either of the identical corpus cavernosums. The three groups of tissues, the two cavernosa and the spongiosum, are expandable sponge-like structures involved in the process of an erection. The corpus spongiosum penis corresponds to the female vestibular bulbs. It contains the urethra 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 semen or urine transporting tube known as the urethra, and extends and ends at the vertical urethral orifice. This third mass of tissue mainly prevents compression of the urethra during penile erection. It singularly lies beneath the corpora cavernosa and holds little of the blood involved during an erection, since most of it goes to fill the paired masses above it.
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In Depth: Corpus spongiosum penis