Those random boners are caused by an overload of hormones, so your body literally tricks your brain into thinking you're aroused.
Anyway, there is always blood in the penis; just like Coutts said, blood flows through the entire body. When you get an erection, your body pumps way more blood into your penis, much more than when you are flacid, thereby making your penis erected.
And I'm really small when flacid, so when I get an erection mine just goes straight up, right up against my zipper and all that good stuff, and it f*cking HURTS. I have to nudge it down my leg.
Anyway, there is always blood in the penis; just like Coutts said, blood flows through the entire body. When you get an erection, your body pumps way more blood into your penis, much more than when you are flacid, thereby making your penis erected.
And I'm really small when flacid, so when I get an erection mine just goes straight up, right up against my zipper and all that good stuff, and it f*cking HURTS. I have to nudge it down my leg.