Pharyngeal Cavity
The pharyngeal cavity is a fibro-muscular tube that can be divided into three regions: the nasopharynx (the part behind the nose), the oropharynx (the part behind the mouth), and the laryngopharynx (a.k.a. the hypopharynx, the part behind the larynx) (Box 1.22). The tube has several gates or valves — an opening into the nasal cavity through the velopharyngeal valve, an opening into the oral cavity through the lingual-velar valve, an opening into the airway through the laryngeal aditus, and an opening into the esophagus through the upper esophageal sphincter (UES, also known as the pharyngo-esophageal segment). Other structures of interest in the pharynx include the base of tongue and the epiglottis.
Box 1.22. Regions of the Pharyngeal Cavity
Box 1.23. Pharyngeal Spaces
Pharyngeal Spaces
If pharyngeal structures have not been altered by age or disease, there are two spaces in the pharynx where food or liquid may rest (Box 1.23). In the laryngopharynx, the juxtaposition of the epiglottis with the base of tongue, at the point of the hyoid bone, creates a pocket known as the vallecula space. (Note: Vallecula are crevices that can be located throughout the body. We are interested in the vallecula in the pharynx.) This space is mostly obliterated during the swallow when the epiglottis inverts.
On either side of the thyroid lamina there are sinus cavities known as the pyriform sinuses. These two pockets sit just superior to the upper esophageal sphincter (UES). Adequate UES opening and timing of the opening, combined with sufficient pharyngeal pressure, will keep the pyriform sinuses relatively free of bolus after the swallow is complete.
Clinical Note
If the pressure in the inferior pharynx increases and the CP muscle neglects to relax in time, the increased pressure at the intersection between the two muscle bellies of the IPC can be easily dissected. The resulting pocket is referred to as Zenker’s Diverticulum. Watch the video below and note the Zenker’s indicated with a red arrow.
Pharyngeal Muscles
The pharyngeal tube contains three important constrictor muscles: superior pharyngeal constrictor (SPC), middle pharyngeal constrictor (MPC), and inferior pharyngeal constrictor (IPC) muscles (Box 1.24). The SPC muscle has multiple insertion points; this muscle goes from the pterygoid-mandibular raphe to the pharyngeal raphe and root of the tongue. The action of the SPC is to collapse the upper part of the pharyngeal tube. The inferior fibers of the SPC muscle make up the glossopharyngeal muscle. The MPC muscle goes from the hyoid bone to the medial pharyngeal raphe. The SPC and MPC muscles are innervated by the pharyngeal plexus.
Box 1.24. Pharyngeal muscles
The IPC muscle goes from the medial pharyngeal raphe to the thyroid and cricoid cartilages. Thus, IPC muscle is comprised of two muscle bellies. The upper fibers which originate from the thyroid cartilage is the thyropharyngeal belly of IPC. Both bellies insert on the medial pharyn