Celiac disease is a medical condition in which the absorptive surface of the small intestine (see below) is damaged by a substance called gluten. This results in an inability of the body to absorb nutrients: protein, fat, carbohydrates, vitamins and minerals, which are necessary for good health.

(photo from www.celiaccentral.org)

The small intestine is the site where most of the nutrients from ingested food are absorbed and is covered in wrinkles or folds called plicae circulares. These are considered permanent features in the wall of the organ. They are distinct from rugae which are considered non-permanent or temporary allowing for distention and contraction. From the plicae circulares project microscopic finger-like pieces of tissue called villi. The small intestine is lined with simple columnar epithelial tissue. The epithelial cells also have finger-like projections known as microvilli. The function of the plicae circulares, the villi and the microvilli is to increase the amount of surface area available for secretion of enzymes and absorption of nutrients.

Gluten is a protein found in wheat, rye, triticale, barley. In the case of wheat, gliadin has been isolated as the toxic fraction. It is the gluten in the flour that helps bread and other baked goods bind and prevents crumbling. This feature has made gluten widely used in the production of many processed and packaged foods.

At present there is no cure, but celiac disease is readily treated by following the gluten-free diet.

(celiac.ca)