The Intestine – Anatomy, immunology, barrier function, microbiome and central regulations

The intestine, with its complex anatomy and intricate physiology, plays a fundamental role in maintaining overall health and well-being. Understanding the diverse functions of the intestine and the factors that can disrupt them is crucial for preventing and managing a wide range of diseases and pathological conditions. This review article explores the multifaceted role of the intestine in regulating human health across physiological and pathological states. A systematic search for relevant literature was conducted using the following electronic databases: PubMed, Web of Science, Scopus, and Google Scholar. The search terms included a combination of keywords related to the intestine, its functions, and relevant conditions (e.g., “intestine”, “mucosa”, “gut barrier dysfunction”, “microbiome”, “gut-brain axis”, “central regulations”, “bacterial translocation”). For this review, we included only peer-reviewed, full-text articles published in English that directly addressed the intestine’s role in regulating human health across physiological and pathological states. This review explores the intestine’s unique structure and its critical neuroregulatory connection with the brain, the gut-brain axis (GBA). Subsequently, we focus on the pathological consequences of gut barrier dysfunction and the microbiome’s contribution to both intestinal and extraintestinal health. Finally, we address the processes activated within the intestine during stress responses.