The bulb of the penis is an enlarged mass of erectile tissue that is located in the midline of the root and is traversed by the male urethra.

It continues as a long cylindrical body on the ventral aspect of the shaft called corpus spongiosum.

They continue into the dorsal aspect of the shaft forming the two corpora cavernosa that are separated by the septum of the penis.

[5] Each crus is covered by the ischiocavernosus muscle which helps maintain an erection by contracting to force blood from the crura into the corpora cavernosa.

The bulb is surrounded by the bulbospongiosus muscle which contracts to help empty the urethra of any residual semen and urine.