Corpus: Pharyngeal isthmus

The isthmus faucium is a narrow passage formed by the palatal arches that marks the transition from the oral cavity (cavum oris) to the pharynx (pharynx) or the pars oralis pharyngis.

The isthmus faucium is bounded by the following structures:

• cranial: velum palatinum (soft palate) with uvula (uvula)
• lateral: arcus palatoglossus (anterior palatal arch, mucosal fold raised by the palatoglossus muscle) and arcus palatopharyngeus (posterior palatal arch, raised by the palatopharyngeus muscle)
• caudal: base of the tongue

The isthmus faucium is narrowed by a contraction of the palatoglossus muscle. On both sides of the isthmus, between the two palatine arches, lie the tonsillar fossae with the palatine tonsils located in them.

In the case of inflammation of the palatine tonsils (tonsillitis), the isthmus faucium can be constricted by the swollen lymphatic tissue. This usually leads to significant swallowing difficulties.