Composition, function, and detection methods of the intestinal barrier

The intestinal barrier represents a fundamental defense system against environmental insults, and its disruption is increasingly recognized as a central contributor to the pathogenesis of diverse diseases. This review provides a comprehensive analysis of intestinal barrier function, highlighting its pivotal role in maintaining physiological homeostasis. We delineate the structural components and regulatory mechanisms that safeguard barrier integrity, and examine the factors that precipitate barrier dysfunction and their implications for disease progression. Particular emphasis is placed on the gut-brain, gut-eye, and gut-liver axes, which mediate the systemic consequences of barrier impairment on overall health. Additionally, we critically evaluate current methodologies for assessing intestinal barrier integrity, discussing their respective advantages and limitations. By synthesizing these insights, this review aims to guide the selection of appropriate investigative approaches, thereby facilitating advancements in disease prevention and therapeutic strategies. Ultimately, this work seeks to deepen understanding of intestinal barrier dynamics and to inform future directions in this rapidly evolving field.