The superior constrictor pharyngis muscle is a skeletal muscle of the pharynx and consists of four parts. It closes the entrance to the nose during swallowing. Paralysis of the soft palate and certain neurologic diseases can disrupt the closure and contribute to dysphagia.
What is the superior pharyngis constrictor muscle?
The superior constrictor pharyngis muscle, or upper pharyngeal constrictor, is located in the throat and is responsible, along with other muscles, for constricting the pharynx. This action is required during swallowing to prevent fluid or food from entering the junction with the nose. In addition to the superior constrictor pharyngis muscle, the pharyngeal musculature possesses two other constrictor muscles, namely the middle and inferior pharyngeal constrictors (musculus constrictor pharyngis medius and musculus constrictor pharyngis inferior). They arise during embryonic development from the third, fourth and sixth gill arches. For this reason, the musculus constrictor pharyngis does not form a uniform tissue, but has the characteristic tripartite division. Like the other pharyngeal muscles, the superior constrictor pharyngis muscle belongs to the striated musculature of the human body.
Anatomy and structure
The basic structure of the constrictor pharyngis superior muscle forms a quadrangular surface and can be structurally divided into four areas, each with a different origin. The single insertion of the pharyngeal muscle is at the pharyngeal suture (raphe pharyngis), where the constrictor pharyngis medius muscle and the constrictor pharyngis inferior muscle also terminate. The pars pterygopharyngea of the Musculus constrictor pharyngis superior arises from the Hamulus pterygoideus ossis sphenoidalis, which belongs to the skull base, where it is associated with the sphenoid bone or wasp bone (Os sphenoidale). In contrast, the pars buccopharyngea arises from the pterygomandibular raphe, which is adjacent to the pterygoid hamulus. On the other side of the pterygomandibular raphe, on the other hand, is the linea mylohyoidea, which belongs to the mandible. At the linea mylohyoidea arises the third part of the musculus constrictor pharyngis superior, the pars mylopharyngea. The fourth and final section of the pharyngeal muscle is the pars glossopharyngea. Its origin is at the musculus transversus linguae, which is a tongue muscle. The superior constrictor pharyngis muscle receives nerve signals from the ninth cranial nerve (glossopharyngeal nerve) as well as from the tenth cranial nerve (vagus nerve). Fibers from both nerve pathways meet in a plexus of nerves in the pharynx: the pharyngeal plexus.
Function and tasks
The function of the superior pharyngeal constrictor muscle is to close the nasopharynx during swallowing so that no fluid or food can enter and the contents of the mouth instead end up entirely in the esophagus. Nerve fibers from the pharyngeal plexus signal the constrictor pharyngis superior muscle to contract. When the pharyngeal muscle tenses, a bulge forms in the nasopharynx (epipharynx). This bulge is also known as Passavant’s annular bulge. The superior constrictor pharyngis muscle pulls the Passavant’s annular bead toward the soft palate, and the soft palate must be in a horizontal position. The soft palate elevator (Musculus levator veli palatini) and the soft palate tensor (Musculus tensor veli palatini) are responsible for its positioning. The larynx must also be closed during swallowing – this task is performed by the thyrohyoid muscle. During swallowing, many muscles must work together in a coordinated manner. Control originates in an area of the brain known as the swallowing center because of its function, located in the medulla oblongata. The swallowing center does not form a tissue structure that is clearly delineated anatomically, but rather a functional network of nerves distributed throughout different areas of the brain. Some parts of the swallowing center are also located in the cerebrum.
Diseases
During the act of swallowing, the role of the superior constrictor pharyngis muscle is to form Passavant’s annular bead and pull it toward the soft palate. The process helps to close the access to the nose. In the setting of soft palate paralysis, this process may be disrupted. One possible cause of soft palate paralysis is the infectious disease diphtheria.This is a bacterial disease that affects the upper respiratory tract. Discomfort when swallowing and sore throat are usually the first signs, along with fatigue, malaise and fever. A coating typically develops in the throat with diphtheria, ranging in color from white to yellowish. In addition, the lymph nodes may swell. In addition to soft palate, other sequelae such as croup and inflammation of the heart muscle (myocarditis) are also possible. As a result of soft palate paralysis, the upper gavage and the soft palate elevator and tensioner can no longer close the upper pharynx, and fluid or food can enter the nasal cavity. Paresis of the soft palate, however, need not be due to diphtheria. It may, in addition, be due to damage to the vagus nerve, as is possible in certain brainstem syndromes. These include Wallenberg syndrome and Jackson syndrome, both of which can occur as a result of stroke. A stroke or cerebral infarction results from a circulatory disturbance in the brain, often because of the (partial) occlusion of a supplying artery. Parts of the brain are undersupplied in a stroke and can suffer irreversible damage if the deficiency condition persists too long. Neurodegenerative diseases also damage the swallowing center in some cases. Corresponding symptoms are common in multiple sclerosis and Parkinson’s disease. Injuries and tumors are also considered causes of lesions of the swallowing center. Nerve damage, however, can also occur only in the course of the innervating nerve pathways, for example, at the pharyngeal plexus.
