The pharyngeal constrictor is a muscle that constricts, or narrows, the pharynx, which is a section of the throat stretching from the mouth and nasal cavities to the larynx. There are actually three pharyngeal constrictors: the superior pharyngeal constrictor muscle, the middle pharyngeal constrictor muscle and the inferior pharyngeal constrictor muscle.
Each of the aforementioned muscles relaxes when the pharynx receives food. When the pharynx descends, the constrictor muscles draw on the food and send it toward the esophagus, where it is transported downward in the gastrointestinal tract. Thus, the pharyngeal constrictor muscles are essential for swallowing.
Located at the rear section of the side of the face is the superior constrictor muscle, which is a quadrilateral muscle consisting of four parts. The pterygopharyngeal part comes from the lower region of the medial pterygoid plate. The buccopharyngeal part arises from the pterygomandibular ligament. The myolopharyngeal part originates from the alveolar process of the mandible, or lower jaw, where the teeth are located. The glossopharyngeal part starts from the tongue's fibers.
This particular constrictor muscle inserts into two areas. One of them, the pharyngeal raphe, also serves as the insertion site for the other constrictor muscles. The other area is the pharyngeal tubercle, which gives the pharyngeal raphe its attachment.
The superior constrictor muscle is paler and thinner than the other two constrictor muscles. One of them, the middle constrictor muscle, is located below it at the upper region of the neck. It chiefly arises from the hyoid bone, a horseshoe-shaped structure situated below the lower jaw. It is notable for its fan-like shape and is smaller than the inferior constrictor muscle below it.
As the thickest of the three pharyngeal constrictor muscles, the inferior constrictor muscle is located farther down the neck. It consists of two parts. The thyropharyngeal part comes from the thyroid cartilage; and the cricopharyngeal part is so named because it arises from the cricoid cartilage.
The pharyngeal constrictor muscles get their innervation from the pharyngeal plexus. This is the collection of nerve fibers that innervates the pharynx in addition to the larynx, or voice box; and the palate, or the roof of the mouth. The specific nerve that innervates the pharyngeal constrictors is the pharyngeal branch of the vagus nerve, which is the pharynx motor nerve and is also called cranial nerve X. Notably, the pharyngeal plexus itself is located at the middle constrictor muscle.