The lining of the human stomach completely replaces itself every three to five days — one of the fastest-renewing tissues in the body — because the same hydrochloric acid that breaks down a tough steak is strong enough to dissolve the stomach wall itself, and continuous regeneration is one part of a layered defense system that keeps the acid from doing damage

You finish a meal. Somewhere inside you, an organ roughly the size of a small melon begins flooding itself with a liquid acidic enough to dissolve metal. The acid is hydrochloric acid, produced by specialised cells in the stomach lining called parietal cells, secreted at a rate of approximately two to three litres per day. [...] The post The lining of the human stomach completely replaces itself every three to five days — one of the fastest-renewing tissues in the body — because the same hydroch