ouch, that smarts

Why is it that when you bite your tongue, you hear a loud *crunch* sound and see stars? And why do tongues have to bleed so dang much anyway? I know blah blah blah blood vessels blah blah blah, but come on. And why when you have bitten your tongue and it is red and sore as the dickens do you continue to nick it with your teeth for days afterward? I know blah blah blah awkward swollen tissue blah blah blah, but still.