Before a single immune cell is called, the body stops almost every microbe at the door. It uses intact skin, moist mucous membranes, chemical secretions, and its own normal flora. Tap a site to see each barrier work. Then switch on a real insult and watch the wall come down.
The barrier map
Tap a numbered site, or an item in the list.
SkinMucous membranesSecretionsNormal floraBarrier down
How much still gets stoppedlive model
99.92percent of microbes stopped
Barriers holding
7 of 7
Getting through
845 in a million
Risk
low
Every barrier is intact. Almost nothing gets past the wall.
The first line of defensefour kinds of barrier, working before you feel a thing
The seven barrier sites
Switch on an insulttap to toggle
Each one knocks out a real barrier. Tap again to put it back.