Along with the other longitudinal pharyngeal muscles (palatopharyngeus, and salpingopharyngeus), the stylopharyngeus muscle causes pharyngeal shortening and plays an important role in pharyngeal clearance. ĭuring the surgery for neurogenic tumor of the cranial nerves, the superior control of the internal carotid artery can be achieved by dissecting the area present between the stylopharyngeus muscle and the styloglossus muscle. In such cases, stylopharyngeus muscle and the styloglossus muscle can be considered as the safe posterior boundary during dissection as they protect the significant anatomic structures of the retrostyloid space. Their growth may displace other significant anatomic structures posteriorly. The presence of any deep-lobe parotid tumors or any ectopic salivary gland tumors specifically occupies the prestyloid space. Thus, this diaphragm acts as a hammock for the submandibular and the parotid glands.Īlso, the stylopharyngeus septum divides the parapharyngeal space into two compartments (retrostyloid and prestyloid). The superior border of this diaphragm divides the parotid gland area in the anterior region and the retrostyloid structures in the posterior region. The inferior border of this diaphragm divides the submandibular gland area in the anterior region and the carotid vessels in the posterior region. While entering the pharyngeal spaces, this septum is considered to be an important surgical landmark. The stylopharyngeus muscle forms a part of a significant anatomical structure known as stylopharyngeal septum (styloid diaphragm). Their function is to pull the tonsillar bed dorso-superiorly. Unlike the descending bundle, the additional insertion does not contribute to pharyngeal clearance. The incidence of occurrence of this additional muscle is high in females compared to that in males this may be the result of aging, which may cause degenerative changes in the main stylopharyngeus muscle (descending bundle). These muscle fibers are short in the course and intermingle with the palatopharyngeus muscle and the superior constrictor of the pharynx. Studies have also reported the presence of an additional muscle sheet of the stylopharyngeus muscle that inserts into the tonsillar bed. These supernumerary muscles have been thought to play a role in abnormal swallowing, pharyngeal clearance, phonetics, modulation of respiration, obstructive sleep apnoea, and dysphagia. Apart from the petropharyngeus, other variations of the stylopharyngeus muscle may also be present such as the occipitopharyngeus, mastoidopharyngeus, and the azygopharyneus. This muscle is known as the petropharyngeus muscle. Various studies have mentioned the presence of the supernumerary muscles of the pharynx that originate from the petrous portion of the temporal bone and get inserted on the superior constrictor muscle. The ninth cranial nerve curves around the posterolateral border of the stylopharyngeus muscle to pass between the superior and middle constrictor muscles and reach the tongue. The lateral border of this recess (lateral glossoepiglottic fold or pharyngoepiglottic fold) is composed of the stylopharyngeus muscle and the palatopharyngeus muscle. The stylopharyngeus muscle has a topographical relationship with the piriform recess, which is the major route for pharyngeal swallowing and serves as the largest pocket providing post-deglutition retention. Some fibers merge with the lateral glossoepiglottic fold while others join with the fibers of the palatopharyngeal muscle and insert into the posterior border of the thyroid cartilage/lamina. Some of the fibers of the stylopharyngeus muscle become lost in the superior and middle constrictor muscles. On the lateral pharyngeal wall, the stylopharyngeus muscle lies posterior to the superior constrictor muscle and anterior to the buccopharyngeal fascia. During its course, it penetrates the pharyngeal wall between two pharyngeal muscles (superior constrictor and the middle constrictor). There it runs in a longitudinal direction running deep to the superior constrictor muscle and superficial to the middle constrictor muscle. It runs in a downward direction between the external and the internal carotid arteries. It is the only pharyngeal muscle that has an origin outside the pharyngeal wall. The stylopharyngeus muscle originates from the medial side of the base of a bony projection from the temporal bone, i.e., the styloid process.
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