Corpus cavernosum of penis

Each corpus cavernosum begins as a crus attached to the ischiopubic ramus and perineal membrane, covered by ischiocavernosus. The crura converge beneath the pubic symphysis and run side by side along the dorsum of the penis to end bluntly under the glans. They are separated by an incomplete septum (pectiniform), so they fill and function as a single unit.

Internally, a meshwork of trabeculae of smooth muscle and fibroelastic tissue, lined by endothelium, encloses vascular spaces (cavernous sinusoids). The deep (cavernosal) artery runs centrally in each corpus and gives coiled helicine arteries that open into the sinusoids. When the smooth muscle relaxes, the sinusoids fill and expand against the thick, inelastic tunica albuginea (≈2 mm), compressing the emissary veins and trapping blood — producing intracavernosal pressures near systolic arterial pressure, further raised by contraction of ischiocavernosus.