Tarmabsorbering

Tarmabsorbering is the process by which substances pass from the lumen of the gastrointestinal tract into the body's internal compartments, primarily the bloodstream or the lymphatic system. The term is used in several Nordic languages and is essentially synonymous with the English expression intestinal absorption.

Absorption occurs by transcellular routes, where substances cross the apical and basolateral membranes of enterocytes, often via specific transport proteins (for example SGLT1 for glucose, PEPT1 for peptides) or by passive diffusion for small lipophilic molecules. Paracellular absorption takes place between adjacent cells through tight junctions and is generally limited to small ions and water. Dietary lipids are absorbed after emulsification and re-esterified into triglycerides within enterocytes, then packaged into chylomicrons for lymphatic transport.

Most absorption occurs in the small intestine—duodenum, jejunum, and ileum—where villi and microvilli create a large surface area. The colon also absorbs water and electrolytes and ferments undigested material, producing short-chain fatty acids that can be absorbed.

Absorption is influenced by physicochemical properties (solubility, ionization, stability), physiological conditions (pH, gastric emptying, motility), and formulation or drug interactions. Measuring the extent of absorption is typically expressed as bioavailability. Malabsorption can result from diseases such as celiac disease, pancreatic insufficiency, or inflammatory bowel disease, and can lead to deficiencies and diarrhea.

Clinical relevance includes nutrition management, pharmacokinetics considerations for oral medications, and diagnosis of malabsorption syndromes. In research, tarmabsorbering is studied via tracer methods, intestinal biopsy, or breath tests to assess absorption capacity or specific transporter function.