Isthmus of fauces

The isthmus of the fauces (or oropharyngeal isthmus) is the narrow opening that connects the oral cavity proper with the oropharynx. Often the terms 'isthmus of fauces' and 'fauces' are used interchangeably, however, there is a slight anatomical difference. The fauces refers to the region connecting the oral cavity proper with the oropharynx, whereas the isthmus of fauces refers to the opening within the fauces that connects oral cavity proper with the oropharynx. It represents the passage through which food, fluids, and air pass from the mouth into the pharynx.

Boundaries

The isthmus of fauces is bounded superiorly by the soft palate and uvula, inferiorly by the posterior part of the tongue, and laterally by the right and left palatoglossal and palatopharyngeal arches, which contain the palatoglossus and palatopharyngeus muscles, respectively.

During swallowing, contraction of the palatoglossus muscles narrows this opening to help prevent regurgitation of food into the oral cavity.

Clinical correlate

The isthmus of fauces is clinically important because inflammation or enlargement of nearby structures, particularly the palatine tonsils, may obstruct the passage and interfere with swallowing or speech.