Intestinal villi
Microscopic folds in the lining of the small intestine that multiply the surface available for absorption, and whose destruction characterises coeliac disease.
Intestinal villi are fine, finger-shaped folds that line the inside of the small intestine. Each one is itself covered with microvilli, forming what is known as the brush border.
This architecture has a single purpose: surface area. A smooth tube of the same length would offer a few tens of square centimetres for exchange; with villi and microvilli, the absorptive surface of the small intestine reaches several tens of square metres. This is what makes it possible to take up nutrients within a few hours of transit.
Their destruction is the very mechanism of coeliac disease. In predisposed people, gluten triggers an immune reaction that flattens the villi (villous atrophy). The absorptive surface collapses, leading to multiple deficiencies, fatigue, anaemia and stunted growth in children, well beyond simple digestive upset.
The good news is their capacity to regenerate: intestinal cells renew themselves within a few days, and strict avoidance of gluten allows the villi to regrow gradually, over several months to a few years. Other situations can damage them: severe infections, parasitic infections, undernutrition and certain treatments.