The Muscles of the Pharynx
There are six muscles which play a role in the function of the pharynx; three are circular and are constrictors, and three are longitudinal in orientation and form an inner muscular ring. The three major muscles which constrict the pharynx are the superior pharyngeal constrictor (SC), the middle pharyngeal constrictor (MC), and the inferior pharyngeal constrictor (IC). The arrangement of these muscles has been compared to three stacked flowerpots as they form a circular pattern one on top of the other. The SC connects the lingula of the mandible (lower jaw bone) to the hamulus (hook-like end) of the medial pterygoid plate. The MC originates from the hyoid bone’s greater horn and is palpable upon examination. The IC is connected to the thyroid gland and nearby cartilage and continues along with the oesophagus. All three constrictors join in the middle to form the seam known as the pharyngeal raphe. There are gaps formed by these three muscles to allow for certain structures to pass through.
Pharynx Muscles can Effect Nerve Function
Above the SC the auditory tube, the levator palati, and the ascending palatine artery pass. Between the SC and the MC there are gaps to accommodate the stylopharyngeus muscle and the glossopharyngeal nerve. The internal laryngeal branch of the superior laryngeal nerve passes through a gap between the MC and IC along with the superior laryngeal artery from the superior thyroid artery. Finally, below the IC, the inferior laryngeal nerve and the inferior laryngeal artery are granted passage through the muscle. It is clear from this complex arrangement that stresses, strains, inflammation, and dysfunction of the muscles in this region can have significant ramifications for nerve function and circulation both to the pharynx itself but also the larynx and the thyroid. Conversely, inflammation or dysfunction in either of the latter two structures can affect pharyngeal function.
Pharynx Inner Muscle
The pharynx also has an inner muscular layer formed by three small, longitudinal, muscles called the stylopharyngeus, palatopharyngeus, and salpingopharyngeus. The former originates outside the pharynx from the styloid process and, as mentioned above, passes through SC and MC. The palatonpharyngeus runs from the palate, down the length of the pharynx and intermingles with the stylopharyngeus’ fibers. The salpingopharyngeus is commonly considered a part of the palatopharyngeus with a different origin: at the opening of the auditory tube at the posterior of the nasal cavity.
These muscles work together to both propel food down the pharynx and into the oesophagus and to act as a sphincter in preventing air from entering the digestive system. The constrictor muscles have a peristaltic, successive, action to move a food bolus down the pharynx, and the longitudinal muscles help to elevate the pharynx upon swallowing so as to aid the bolus to be engulfed.
Last Updated: 1/11/2011