Oral mucosa

The oral mucosa is the moist lining of the mouth, a thin tissue rich in blood vessels through which some substances can pass directly into the bloodstream.

It covers the cheeks, gums, palate, floor of the mouth and the underside of the tongue, and varies from a tough, keratinized surface on the gums and hard palate to a thin, non-keratinized lining under the tongue and inside the cheeks. That thin lining sits over a dense network of capillaries that drain into veins leading to the general circulation rather than to the liver, so substances absorbed there avoid the first-pass metabolism that reduces many swallowed compounds.

This is the basis for sublingual and buccal dosing routes, in which a liquid or dissolving tablet is held under the tongue or against the cheek. How much of a cannabinoid actually crosses the mucosa depends on contact time, the formulation and saliva flow, and much of a held liquid is eventually swallowed anyway. The mucosa is also the site of common conditions such as aphthous ulcers and gingivitis, and it is examined visually and by touch in routine dental care.