The corpora cavernosa and the corpus spongiosum have separate tunical layers. The CS tunica is not as tough as the CC tunica.
From the Boston Medical Center Insitute for Sexual Medicine web site :
"The tunica albuginea forms a thick fibrous coat to the spongy tissue of the corpora cavernosa and corpus spongiosum. It consists of two layers, the outer longitudinal and the inner circular. The tunica albuginea becomes thicker centrally where it forms a groove to accommodate the corpus spongiosum. As the crura diverge proximally, the circular layer provides the support. The corpora are separated in the center by an intercavernous septum. The septum is incomplete distally, perforated on its dorsal margin by vertically orientated openings in the pectiniform septum that provides communication between the corpora. Along the inner aspect of the tunica albuginea, numerous flattened columns or sinusoidal trabeculae composed of fibrous tissue, elastin fibers and smooth muscle surround the endothelium-lined sinusoids or cavernous spaces. In addition, a row of structural trabeculae arises near the junction of the three corporal bodies and inserts in the wall of the corpora about the midplane of the circumference. The tunical albuginea provides a tough uniform backing for the engorged sinusoidal spaces. The tunical albuginea of the corpus spongiosum is thinner and contains smooth muscles that aid ejaculation. The glans is devoid of tunica albuginea. The corpus spongiosum becomes bulbous where it is covered by the bulbospongiosus to form the urethral bulb."
