[quote name='Eviltude']FYI, the penis isn't a muscle, so you can't "exercise" your penis.
Sorry, boo.[/quote]
penile erectile tissue, or the corpora cavernosa, meaning cave-like bodies, are sponge-like erectile tissue. it's made of endothelium and connective tissue.
[/former anatomy professor]
hey jmepo - see, i know stuff other than butthole trivia.