Wikipedia, which may be where you got the 10mA thing from, tells us that the human body's resistance is something like 100,000 Ohms.

Applying that to Ohm's Law (V=IR or I=V/R) as lefty rightly (haha) points out above, gives us 5 / 100000 = 0.00005 Amps which if I counted the zeroes correctly is 5E-5 or 50 microAmps. Certainly very small...

If it worked the way you thought, ie that current is pushed as opposed to pulled as lefty pointed out, and 5V at 40mA was lethal, how would anybody survive touching a 12V car battery which can supply 100s of Amps?