The isthmus of the pharynx consists of the upper uvula and the free edge of the soft palate, the lower dorsum of the tongue, the lingual palatal arches or pharyngeal palatal arches on both sides, which together form a circumferential and narrow portion. The isthmus of the pharynx is situated in the oropharynx, also known as the mesopharynx, and is the backward continuation portion of the oral cavity, which is situated between the plane of the soft palate and the plane of the upper edge of the epiglottis, and the so-called pharynx is usually referred to as this area. The posterior wall is flat against the 2nd-3rd cervical vertebrae, with scattered lymphoid follicles under the mucosa, and the anterior part is connected with the oral cavity through the isthmus of the pharynx, and the apical part is bounded by the plane of the soft palate and the plane of the upper edge of the epiglottis, and is divided into the three parts of the nasopharynx, the oropharynx, and the laryngopharynx from the top down.