Corpus spongiosum (also known as corpus cavernosum urethrae in older texts) is the mass of spongy tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 surrounding the male urethra

Urethra

In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...

 within the penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

. Although called corpus cavernosum in older texts, this is not correct.

Anatomy

Behind, it is expanded to form the urethral bulb, and lies in apposition with the inferior fascia of the urogenital diaphragm, from which it receives a fibrous investment.

The urethra enters the bulb nearer to the superior than to the inferior surface. On the latter there is a median sulcus (groove), from which a thin fibrous septum (wall) projects into the substance of the bulb and divides it imperfectly into two lateral lobes or hemispheres.

The portion of the corpus spongiosum in front of the bulb lies in a groove on the under surface of the conjoined corpora cavernosa penis. It is cylindrical in form and tapers slightly from behind forward. Its anterior end is expanded in the form of an obtuse cone, flattened from above downward. This expansion, termed the glans penis

Glans penis

The glans penis is the sensitive bulbous structure at the distal end of the penis. The glans penis is anatomically homologous to the clitoral glans of the female...

, is moulded on the rounded ends of the corpora cavernosa penis, extending farther on their upper than on their lower surfaces.

At the summit of the glans is the slit-like vertical external urethral orifice

External urethral orifice

External urethral orifice can refer to:* External urethral orifice * External urethral orifice...

, also known as the meatus

Meatus

In anatomy, a meatus is a natural body opening or canal .Examples include:* the external acoustic meatus, the opening of the ear canal...

.

The circumference of the base of the glans forms a rounded projecting border, the corona glandis, overhanging a deep retroglandular sulcus (Meiring's sulcus), behind which is the neck of the penis.

Function

The function of the corpus spongiosum in erection is to prevent the urethra from pinching closed, thereby maintaining the urethra as a viable channel for ejaculation. To do this, the corpus spongiosum remains pliable during erection while the corpora cavernosum penis becomes engorged with blood.