The penis is a cylindrical-shaped mass of erectile tissue surrounded by fibrous tissue called tunica albuginea. During sexual arousal the permeated blood tissues (corpus spongiosum and the paired corpus cavernosum) fill with blood from the deep artery to produce an erection. The penile (spongy) urethra serves as a passageway for sperm ejaculation and urine excretion. The dorsal nerve accompanies a neurovascular bundle located superior to the corpus spongiosum and corpus cavernosum. Label the structures of this cross-section of the penis..