**4. Microbiota**

The organization of the small intestine is in the form of a model of strata formed through the creation of the intestinal barrier in which two layers are located, one "external" (consisting of the microbiota, the mucous layer, and the intestinal epithelium) that acts as an anatomical and, therefore, physical barrier, preventing their adhesion and other more "internal," mainly formed by the GALT (gut-associated lymphoid tissue), responsible for the production of the immune response and tolerance mechanisms. The correct interrelation between both layers contributes to maintaining proper functioning of the small intestine, actively ensuring its intestinal permeability.

The microbiota contributes to the digestion and recovery of energy from dietary waste and the production of vitamins and hormones. It prevents the growth of pathogenic bacteria, increasing its protection and local defense. It also contributes to trophism, favoring the production of mucin, as well as the proliferation and

differentiation of the intestinal epithelium. It also exerts immunological functions, participating in the development and maturation of the immune system [3].
