läpäisyreittien

Läpäisyreittien (läpäisyreittejä) is a Finnish term referring to the permeation or transmission routes by which substances, pathogens, or signals can cross barriers separating compartments, such as outside the body and the bloodstream, or a cell membrane. The concept is used in several disciplines, notably pharmacology, toxicology, medicine, and epidemiology.

In pharmacology, läpäisyreittien describes how a substance enters the body and reaches its target. Common routes include transcellular (through cells), paracellular (between cells via tight junctions), and carrier-mediated transport. Lipid solubility, molecular size, charge, and the presence of transport proteins or receptors influence permeability and bioavailability. Absorption can occur in the gut, skin, or lungs, and is affected by formulation, pH, and blood flow.

In epidemiology, läpäisyreitti refers to how a pathogen or infectious agent passes from one host or environment to another. Typical transmission pathways include direct contact, droplets, airborne spread, fecal–oral routes, vector-borne transmission, and sexual transmission. Transmission efficiency depends on pathogen characteristics, host susceptibility, and environmental conditions; control measures target breaking specific routes, for example ventilation to reduce airborne spread, hand hygiene for contact transmission, or vaccination.

In research and materials science, the term may also describe diffusion through barriers such as membranes, describing factors like diffusion coefficients, thickness, and partitioning.