Darmresorption

Darmresorption, or intestinal resorption, is the physiological process by which the contents of the intestinal lumen are transported into the body. The small intestine, especially the duodenum and jejunum, is the primary site, with substantial absorption also occurring in the ileum. The large intestine reabsorbs water and electrolytes and participates in some nutrient uptake.

Absorption occurs by transcellular and paracellular routes, via active transport and passive diffusion. Nutrients include carbohydrates (glucose and galactose via SGLT1, then GLUT2), amino acids via dedicated transporters, and fats absorbed as fatty acids and monoglycerides, reassembled into triglycerides and packaged into chylomicrons for lymphatic transport. Bile acids are reabsorbed in the ileum. Vitamins and minerals rely on specific carriers; fat-soluble vitamins accompany fats; water-soluble vitamins use carriers; calcium and iron absorption are regulated by vitamin D and hormonal signals. Water follows osmotically; ions are reabsorbed by active and passive mechanisms.

Regulation depends on the mucosal surface area provided by villi and microvilli, intestinal transit time, and gut hormones such as GLP-2 and cholecystokinin, which influence absorption efficiency. The gut microbiota can affect nutrient availability and bile acid metabolism, indirectly impacting resorption.

Clinical significance: impaired Darmresorption leads to malabsorption syndromes, including celiac disease, Crohn disease, pancreatic insufficiency, and post-surgical changes. Symptoms include chronic diarrhea, weight loss, steatorrhea, and micronutrient deficiencies. Diagnostics may involve fecal fat testing, D-xylose testing, and nutrient-level assessments. Management focuses on treating underlying conditions and, when needed, dietary modification and enzyme replacement therapy.