[Series: Important medical-dental interactions. Oral manifestations in patients with intestinal diseases].

The intestine, consisting of the small and large intestines, is a functional and immunologically active organ in which digestion, absorption, and defence are closely intertwined. Immediately following the stomach is the duodenum, where the food chyme comes into contact with pancreatic digestive juices and bile, enabling further nutrient breakdown. The primary function of the small intestine is the absorption of nutrients through the intestinal mucosa. The large intestine is responsible for the reabsorption of water and electrolytes and is home to a diverse microbiome, consisting of various microorganisms involved in the digestion of complex carbohydrates. This microbiome is constantly interacting with the intestinal immune system, maintaining a delicate balance between tolerance and immune activation. Disruption of this balance can lead to or contribute to various conditions, some of which are discussed in this overview.