When the superior constrictor constricts during swallowing, it forms a prominent ridge on the deep aspect of the pharyngeal wall that catches the margin of the elevated soft palate, which then seals closed the pharyngeal isthmus between the nasopharynx and oropharynx.
The middle constrictor muscles are attached to the lower aspect of the stylohyoid ligament, the lesser horn of the hyoid bone, and the entire upper surface of the greater horn of the hyoid (Fig. 8.202).
Like the superior constrictors, the middle constrictor muscles fan out posteriorly and attach to the pharyngeal raphe.
The posterior part of the middle constrictors overlaps the superior constrictors.
The inferior constrictor muscles attach anteriorly to the oblique line of the thyroid cartilage, the cricoid cartilage, and a ligament that spans between these two attachments to cartilage and crosses the cricothyroid muscle (Fig. 8.202).
Like the other constrictor muscles, the inferior constrictor muscles spread out posteriorly and attach to the pharyngeal raphe.
The posterior part of the inferior constrictors overlaps the middle constrictors. Inferiorly, the muscle fibers blend with and attach into the wall of the esophagus.
The parts of the inferior constrictors attached to the cricoid cartilage bracket the narrowest part of the pharyngeal cavity.
The three longitudinal muscles of the pharyngeal wall (Fig. 8.203 and Table 8.18) are named according to their origins—stylopharyngeus from the styloid process of the temporal bone, salpingopharyngeus from the cartilaginous part of the pharyngotympanic tube (salpinx is Greek for “tube”), and palatopharyngeus from the soft palate. From their sites of origin, these muscles descend and attach into the pharyngeal wall.
The longitudinal muscles elevate the pharyngeal wall, or during swallowing, pull the pharyngeal wall up and over a bolus of food being moved through the pharynx and into the esophagus.
The cylindrical stylopharyngeus muscle (Fig. 8.203A) originates from the base of the medial surface of the styloid process of the temporal bone and descends between the superior and middle constrictor muscles to fan out on, and blend with, the deep surface of the pharyngeal wall. It is innervated by the glossopharyngeal nerve [IX].
The salpingopharyngeus (Fig. 8.203B) is a small muscle originating from the inferior aspect of the pharyngotympanic tube, descending on, and blending into, the deep surface of the pharyngeal wall. It is innervated by the vagus nerve [X].
The palatopharyngeus (Fig. 8.203B), in addition to being a muscle of the pharynx, is also a muscle of the soft palate (see pp. 1098–1099). It is attached to the upper surface of the palatine aponeurosis, and passes posteriorly and inferiorly to blend with the deep surface of the pharyngeal wall.
The palatopharyngeus forms an important fold in the overlying mucosa (the palatopharyngeal arch). This arch is visible through the oral cavity and is a landmark for finding the palatine tonsil, which is immediately anterior to it on the oropharyngeal wall.
In addition to elevating the pharynx, the palatopharyngeus participates in closing the oropharyngeal isthmus by depressing the palate and moving the palatopharyngeal fold toward the midline.
The palatopharyngeus is innervated by the vagus nerve [X].
The pharyngeal fascia is separated into two layers, which sandwich the pharyngeal muscles between them: