Penis and Urethra

Composed of 3 cylindrical shafts

• 2 corpora cavernosa : Main erectile bodies

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    On dorsal surface of penis

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    Diverge at root of penis ( crura ) and are invested by ischiocavernosus muscles

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    Chambers traversed by numerous trabeculae, creating sinusoidal spaces

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    Multiple fenestrations between corpora, creating multiple anastomotic channels

• 1 corpus spongiosum : Contains urethra

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    On ventral surface, in groove created by corpora cavernosa

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    Becomes penile bulb at root and is invested by bulbospongiosus muscle

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    Forms glans penis distally

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    Also erectile tissue but of far less importance

Tunica albuginea forms capsule around each corpora

• Thinner around spongiosum than cavernosa

All 3 corpora surrounded by deep fascia ( Buck fascia ) and superficial fascia ( Colles fascia )

Main arterial supply from internal pudendal artery

• Cavernosal artery runs within center of each corpus cavernosum

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    Gives off helicine arteries , which fill trabecular spaces

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    Primary source of blood for erectile tissue

• Paired dorsal penile arteries run between tunica albuginea of corpora cavernosa and Buck fascia

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    Supplies glans penis and skin

Venous drainage of corpora cavernosa

• Emissary veins in corpora pierce through tunica albuginea → circumflex veins → deep dorsal vein of penis → retropubic venous plexus

• Superficial dorsal vein drains skin and glans penis

Neurologically mediated response eliciting smooth muscle relaxation of cavernosal arteries, helicine arteries, and cavernosal sinusoids

Blood flows from helicine arteries into sinusoidal spaces

Sinusoids distend, eventually compressing emissary veins against rigid tunica albuginea

• Venous compression prevents egress of blood from corpora, which maintains erection