[TA] one of a pair of ridges or folds of mucous membrane that pass downward from the posterior margin of the soft palate to the lateral wall of the pharynx. It encloses the palatopharyngeus muscle and forms the posterior margin of the tonsillar fossa. It also demarcates the isthmus of fauces from the oropharynx. SYN: arcus palatopharyngeus [TA], plica posterior faucium*, posterior pillar of fauces*, pharyngopalatine arch, posterior palatine arch.