The proximal part of the corpus spongiosum 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.

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.

At the summit of the glans is the slit-like vertical opening known as the external urethral orifice, or the urinary meatus.

To do this, the corpus spongiosum remains pliable during erection while the corpora cavernosa penis become engorged with blood.