The penis is composed of three columns of erectile tissue bound together by the tunica albuginea.
Tunica Albuginea – sheath of dense irregular connective tissue that surrounds the erectile bodies.
Corpora Cavernosum (#1 and #2) – a pair of vascular channels located dorsally within the penis.
Walls and trabeculae consist of connective tissue and smooth muscle.
Smooth Muscle – abundant in trabeculae and relaxes during erection.
Helicine Arteries (#1 and #2) – normally coiled, but straighten and dilate on erection.
Blood Sinuses – labyrinth lined with endothelial cells and become filled with blood during erection.
Central Artery (or Deep Artery of the Penis) – each corpus contains a single, central artery.
Corpus Spongiosum – located ventrally within the penis.
Erectile Tissue – similar in structure to the corpora cavernosum but does not become as turgid on erection.
Urethra – lined with a pseudostratified columnar epithelium.
Mucous Glands of Littre and Ducts – secrete a clear mucus on erection.
Superficial Fascia – connective tissue that surrounds the penis with many blood vessels and nerves.