In a nutshell. The D fills up with blood, usually when aroused or stimulation is present. And yes they do happen unintentionally at times this can make for some very awkward situations.
The things filling up with blood are called the Corpus Cavernosum.
ADutchExpression t1_j6hgvqz wrote
Reply to eli5: How do erections work? Do they sometimes happen unintentionally? by [deleted]
In a nutshell. The D fills up with blood, usually when aroused or stimulation is present. And yes they do happen unintentionally at times this can make for some very awkward situations.
The things filling up with blood are called the Corpus Cavernosum.