The gut is a remarkable organ in many respects, not the least of which is its ability to mend itself even when harmed or damaged. The intestinal lining contains cells called enterocytes that are constantly being destroyed by acids and enzymes produced by stomach acid and bacteria living in our digestive system. Enterocytes can also be destroyed by chemicals such as alcohol or drugs, but they can also be regenerated during recovery from illness or injury. When enterocytes are destroyed by disease or inflammation, there is no replacement cell to take their place. This can lead to intestinal damage or ulcers. But enterocytes can also migrate from other parts of the intestine (called "ectopic" migration) to fill in gaps left by dead cells, thus restoring barrier function. If the injured area of the intestine is limited, the body will usually regenerate new enterocytes; however, if there is extensive damage, the patient may require surgery to remove any remaining tissue before healing can occur. In general, the body has two ways to repair damage: through the immune system or through regeneration. The intestinal lining functions as a barrier against harmful substances while allowing nutrients to pass into the bloodstream. When this barrier is compromised, however, pathogens or toxins can seep into the body causing infection or cancer. Healing via regeneration means that the damaged tissue is replaced with new tissue.